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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


URBANA,  JULY,  1898. 


BULLETIN  NO. 


THE  CHEMISTRY  OF  THE  CORN  KERNEL1.  . 

INTRODUCTION. — The  object  of  these  studies  on  the  chemisty  of  corn2 
is  to  trace  its  historical  development,  to  bring  together  from  many 
sources  the  existing  knowledge  of  the  subject,  and,  if  possible,  to  add 
thereto  in  certain  lines  where  our  present  knowledge  seems  most  defi- 
cient, omitting  fields  wherein  other  investigators  are  known  to  be 
engaged.  With  the  single  purpose  of  being  faithful  to  the  history  of 
the  subject,  I  have  felt  equally  free  to  point  out  misconceptions,  erron- 
eous conclusions,  or  real  advances  of  past  investigations.  The  subject 
has  naturally  divided  itself  into  two  parts: 

i st.  The  proximate  composition  of  corn,  which  has  a  very  prac- 
tical significance  as  indicating  its  value  as  food  for  man  and  domestic 
animals  and  as  raw  material  for  various  manufacturing  purposes. 

2nd.  The  complete  and  exact  composition  of  the  different  groups 
of  substances  found  by  proximate  analysis,  a  matter  of  more  purely 
scientific  interest,  though  not  without  phases  of  economic  importance. 

ACKNOWLEDGMENTS. — I  acknowledge  with  pleasure  and  gratitude 
my  indebtedness  to  the  Department  of  Chemistry  of  Cornell  University  for 
the  opportunities  and  privileges  which  have  been  freely  accorded  to  me. 
I  am  especially  grateful  to  Professor  G.  C.  Caldwell,  under  whose  direc- 
tion these  studies  have  been  carried  on,  and  who  has  been  to  me  a  con- 
stant source  of  counsel  and  encouragement. 

1  Presented  to  the  Faculty  of  Cornell  University  as  a  thesis  for  the  degree  of 
Doctor  of  Philosophy,  June,  1898. 

2Indian  corn,  maize;  Ger.  IVillschkorn,  J  fat  is;  Fr.  metis:  Sp.  maiz ;  from  Hay- 
tian  tnahi's.  (Zea  Mays  L.) 


132  BULLETIN    NO.     53. 

Bizio  found  corn  to  contain  oil,  which  had  not  been  discovered 
by  Gorham.  The  substance,  hordein,  was  so  called  by  Bizio  because 
of  its  similarity  to  the  substance  which  had  been  obtained  from 
barley  by  Proust1  and  so  named  by  him;  which,  however,  was  after- 
ward shown  by  Guibourt2  to  be  merely  a  mixture  of  hulls  and  cellular 
tissue;  and  the  hordein  as  found  by  Bizio  was  doubtless  a  mixture  of 
these  fibrous  substances  with  considerable  amounts  of  adhering  starch 
and  protein. 

Probably  the  first  work  from  the  record  of  which  the  total  amount 
of  nitrogenous  matter  can  be  very  approximately  calculated  was  that 
of  Bousingault,  published3  in  1836  upon  the  total  nitrogen  content  of 
corn.  By  combustion  with  copper  oxid  .617  grammes  of  corn  (con- 
taining 18  per  cent,  of  water)  were  found  to  yield  10.3  cubic  centi- 
meters of  nitrogen  gas  measured  at  9  degrees  and  738  millimeters.  By 
computation  I  find  this  to  be  equivalent  to  2.39  per  cent,  of  nitrogen  in 
the  dry  matter,  and  by  using  the  factor  6.25,  this  gives  14.9  per  cent,  of 
protein. 

In  1846  Horsford  reported*  a  complete  ultimate  organic  analysis  of 
corn  and  then  by  an  ingenious  use  of  the  formula  which  had  been 
worked5  out  for  the  average  composition  of  several  proteid  bodies,  as  egg- 
albumen,  gluten  (Kleber)  of  wheat,  rye,  etc.,  he  calculated  the  ultimate 
composition  not  only  of  the  nitrogenous  matter,  but  also  of  the  nitro- 
gen-free organic  matter.  Using  the  factor  6.375  for  converting  nitrogen 
into  protein,  and  having  determined  the  percentage  of  mineral  matter 
he  gives  corn  the  following  composition: 

Carbon , 8 . 07 

Hydrogen i .  oo 

Nitrogenous  matter 14.66         Nitrogen 2.30 

Sulfur 16 

Oxygen 3.13 

Carbon   37.38 

Non-nitrogeuous  organic  matter. 84. 52         Hydrogen 5.61 

Oxygen 41.53 

Mineral  matter 1.92  1.92 


^nnales  de  Chimie  et  de  Physique  (1817),  [i]  5,  337. 

2Jahresbericht  [Berzelius]  iiber  die  Fortschritte  der  physischen  Wissenschaften 
(1831)  10,  202. 

3  Annales  de  Chimie  et  de  Physique  (1836)  [2]  63,  239. 

4Annalen  der  Chemie  und  Pharmacie  (1846)  58,  182. 

•"'Soberer,  ibid.  (1841) 40,  i;  Jones,  ibid.  (1841)40,  65;  Heldt,  ibid.  (1843)  45,  198. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  133, 

A  very  extended  article  by  J.  H.  Salisbury  on  the  general  subject 
of  corn  was  published1  in  1848.  It  included  a  report  of  considerable 
chemical  work,  done  by  such  imperfect  methods  as  nearly  to  deprive  it 
of  permanent  value,  as  will  appear  from  the  following  analysis  of  two* 
samples  of  corn  kernels  : 

I.  2. 

Albumen 9.29  4-64 

Zein 6.73  3.98 

Casein i .  44  .09 

Dextrine  or  gum 5-94  3-53 

Fiber 12.09  .96 

Matter  separated  fromfiber  by  weak  potash  solution,   7.80  6.48 

Sugar  and  extract 13.27  14.42 

Starch 38.28  60 . 92 

Oil 5.18  4.98 

The  methods  employed  by  Salisbury  were  in  the  main  similar  to 
those  of  the  earlier  investigators  and  are  briefly  indicated  as  follows  : 

The  powdered  corn  was  washed  with  water  which  was  decanted. 
The  residue  extracted  with  alcohol  and  dilute  potash  water  gave  the 
fiber.  The  matter  held  in  suspension  in  the  water  was  collected,  washed 
with  alcohol  and  noted  as  starch,  the  residue  from  the  evaporation  of 
the  alcohol  became  a  portion  of  the  "sugar  and  extract."  The  turbid 
water  from  the  starch  determination  was  heated  and  the  coagulated 
matter  called  albumen.  In  one  portion  of  the  filtrate  the  "casein"  was 
precipitated  by  acetic  acid,  and  the  "dextrine  or  gum"  by  alcohol  after 
partial  evaporation.  In  a  second  portion  the  "casein"  and  "dextrine 
or  gum"  were  together  removed  by  alcohol  and  another  portion  of 
"sugar  and  extract"  obtained  by  evaporating  the  filtrate  to  dryness. 

The  zein  and  oil  were  extracted  from  the  corn  by  alcohol  and 
separated  by  ether  after  evaporation  of  the  alcohol. 

Following  Salisbury's  work  proximate  analyses  were  reported  by 
Poison2,  Poggiale3,  Stepf ,  Payen4,  and  also  by  the  renowned  and  but  re- 
cently deceased  R.  Fresenius5. 


'Transactions  of  the  New  York  State  Agricultural  Society  (1848)  8,  678;  Ameri- 
can Journal  of  Science  and  Arts  (1849)  [2]  8,  307. 

-Chimic.  Gazette  (1855)  211  ;  Journal  fiir  praktische  Chemie  (1855)  66,  320. 

3Jahresbericht  [Leibig  und  Kopp]  fiber  die  Fortschritte  der  Chemie  (1856)  809. 

4Journal  fiir  praktische  Chemie  (1859)  76,  88, 

5Landwirtschaftliche  Versuchs-Stationen  (1859)  1,  179;  Jahresbericht  [Hoff- 
mann] uber  die  Fortschritte  auf  dem  Gesammtgebiete  der  Agricultur-Chemie  (1859) 
2,76. 


134  BULLETIN    NO.     53.  [/"6'> 

The  following  will  serve  as  illustrations  of  the  results  : 

Poison.                     Poggiale.  Fresenius. 

Water n.8  dry  13.5  dry  13-46  dry 

Ash 1.8  2.04           1.4  1.62  1.58  1.83 

Protein 8.9  10.09           9-9  xl-44  10.04  11.60 

Oil 4.4  4.99           6.7  7.75  5.11           5.90 

Fiber 15.9  18.03           4-°2  4.62  1.58           1.83 

Sugar 2.Q1  3.29  2.333         2.69 

Starch 54-3  61.56  64.5  74-57  65.90  76.15 

In  1869,  Atwater  reported*  the  following  results  from  a  study5  of  the 
proximate  composition  of  corn  : 

Early  Button.         Common  yellow.  King  Philip. 

Ash 1.66  1.46  1.77 

Protein 10.46  10.86  13.16 

Fat     6.16  4-94  4-93 

Fiber 2.74  2.68  2.45 

Sugar 3.26  5.34  3.38 

Gum 4-59  2.64  5.32 

Starch 7 1  •  1 3  72.08  68 . 99 

The  protein  was  estimated  by  multiplying  the  total  nitrogen  by  the 
factor  6.25,  a  method  which  had  come  into  general  use,  and  which  has 
already  been  referred  to  under  Horsford's  work.  Sugar  was  estimated 
by  Fehling's  method  from  the  aqueous  extract,  and  the  gum  is  the 
difference  between  the  sugar  and  the  dried  aqueous  extract.  The  oil  is 
the  ether  extract.  Fiber  was  determined  by  extracting  with  dilute  acid 
and  alkali,  essentially  the  method  employed  by  Gorham  nearly  eighty 
years  ago,  and  in  general  use  among  agricultural  chemists  of  to-day, 
having  been  known  under  various  names,  as  PeligotV,  Henneberg's,  or 
the  Weende7  method,  the  last  being  common  at  the  present  time.  Starch 
was  estimated  by  difference. 

Closely  following  Atwater's  work  numerous  analyses  were  reported 
by  European  chemists.  In  the  group  of  carbohydrates  only  the  fiber 
was  determined,  the  remainder  being  estimated  by  difference  and  re- 
ported under  the  negative  and  indefinite  heading  "nitrogen-free  extract" 
for  which  I  have  recently  proposed8  to  substitute  the  more  definite  and 
logical  term  carbohydrate  extract. 

*and  gum. 

2  and  loss. 

3dextrine. 

4W.  O.  Atwater — The  proximate  composition  of  several  varieties  of  American 
maize — Thesis  for  the  degree  of  Doctor  of  Philosophy,  Yale  College  (1869)  ;  Ameri- 
can Journal  of  Science  and  Arts  (1869)  [2]  48,  352. 

5The  analysis  of  a  sample  of  sweet  corn  also  reported  is  omitted. 

ejournal  fiir  praktische  Chemie(i85o)  50,  261, 

7Landwirtschaftliche  Versuchs-Stationen  (1864)  6,  497. 

8University  of  Illinois  Agr.  Exp.  Station  Bulletin  (1896)  43 


1898.]  CHEMISTRY  OF  THE  CORN  KERNEL.  135 

The  following  table  gives  a  number  of  the  results  obtained,  all 
being  reduced  to  the  basis  of  dry  matter  : 

Carbohydrate 

Analyst1,                   Ash.         Protein.  Fat.  Fiber.  extract. 

Dietrich 3. 19           13.88  5-59  2.86  74.48 

Nessler 4-53             8.81  5.87  6.24  74-55 

Nessler 3.20            6.41  6.17  6.54  77-68 

Nessler 3.98           10.01  6.25  5-35  74-41 

Kreuzhage 1.70           13-03  4-79  i-74  78.74 

Honig  und  Brimmer 1.50            9.00  4.16  1.58  83.76 

Honig  und  Brimmer 1.42           10.35  4-36  1.55  82.32 

In  1883  Richardson2  made  a  compilation  of  analyses  of  corn  grown 
in  various  parts  of  the  United  States  during  the  years  1877  to  1882. 
The  following  table  shows  the  number  of  samples  analyzed  and  the  aver- 
ages of  the  analyses  from  each  state  represented.  All  dry  matter  other 
than  ash,  protein,  and  oil  I  have  grouped  under  the  general  term 
carbohydrates.  This  is  done  for  several  reasons,  i.  We  are  consider- 
ing not  complete  but  proximate  analysis.  2.  Ash,  protein,  fat,  and 
carbohydrates  constitute  distinctly  different  groups  with  well  known  in- 
dividual properties  or  characteristics  as  to  use,  value,  etc.  3.  The 
amount  of  fiber  in  corn  is  too  small  to  warrant  its  determination  ordi- 
narily, even  if  it  were  known  that  its  value  differs  slightly  from  that  of 
other  carbohydrates,  the  pentosans,  for  example.  4.  The  limit  of  error 
in  fiber  determination  is  wide  and  not  only  appears  in  the  fiber  itself 
but  also  in  the  carbohydrate  extract  (so  called  nitrogen-free  extract.) 
5.  These  data  become  more  readily  comparable  with  my  own  analyses 
which  are  herein  reported  without  fiber  determinations. 

Samples.       Ash.         Protein.  Fat.     Carbohydrates. 


New  Hampshire 1 1 

Vermont i 

Connecticut 13 

Pennsylvania.- 5 

North  Carolina 2 

Kentucky i 

Tennessee i 

Indiana..  .    i 


.76  12.98  6.10  79-i6 

.59  ii. 10  6.16  81.15 

73  n-75  5-27  81.25 

55  9-65  5-67  83.13 

,50  12.03  5-43  81.04 

.62  10.62  5.77  81.99 

•33  10.05  5-51  83.11 


.44  11.84  5-49  81.23 

Michigan 12  1.67  12.83  5.70  79-8o 

Missouri 26  1.83  11.48  5.75  80.94 

Kansas 6  1.69  n-53  5-53  81.25 

Colorado i  1.68  10.95  6.32  81.05 

Texas 20  1.59  11.61  6.09  80.71 

Oregon i  1.61  8.68  7.80  81.91 

Washington i  1.67  9.36  6.39  82.58 

Mexico 3  J.75  IJ.44  6.06  80.75 

General  average 1.69  11.63  5-78  80.90 

^ahresbericht  [Hoffmann]   iiber  die  Agricultur-Chemie  (1872)  15,   10;    (1876) 
19,  7. 

2U.  S.  Dept.  of  Agr.,  Division  of  Chemistry  Bulletin  (1883)  1. 


136  BULLETIN    NO.     53. 

The  following  are  some  of  the  conclusions  which  Richardson  draws 
from  his  data  : 

"There  is  apparently  the  same  average  amount  of  ash.  oil,  and  albuminoids, 
[protein]  in  a  corn  wherever  it  grows,  with  the  exception  of  the  Pacific  Slope,  where, 
as  with  wheat,  there  seems  to  be  no  facility  for  obtaining  or  assimilating  nitrogen. 

"Corn  is,  then,  an  entirely  different  grain  from  wheat.  It  maintains  about  the 
same  percentage  of  albuminoids  under  all  circumstances,  and  is  not  affected  by  its 
surroundings  in  this  respect. 

"Only  two  analyses  have  been  made  from  the  Pacific  Slope  and  more  are 
needed  for  confirmation,  but  as  the  two  analyses,  like  those  of  the  wheats  grown 
there,  are  low  in  albuminoids,  it  may  safely  be  assumed  to  be  a  characteristic  of  that 
portion  of  the  country." 

These  conclusions  scarcely  appear  to  be  warranted  from  the  data. 
By  computation  from  the  114  analyses  of  corn,  I  find  the  total  varia- 
tion in  protein  to  be  63.6  per  cent,  of  the  average  amount  determined; 
while  from  the  260  analyses  of  wheat  referred1  to  by  him  it  is  only  neces- 
sary to  exclude  5  analyses  to  bring  the  total  variation  in  protein  to  60.  i 
per  cent,  of  the  average  amount  determined.  Or  if  we  take  the  averages 
of  the  10  highest  and  the  10  lowest  results  on  the  protein  of  1 14  samples 
of  corn,  12.34  per  cent,  and  8.19  per  cent.,  respectively,  we  find  the 
difference,  4.15  per  cent.,  to  be  40  per  cent,  of  the  general  average; 
while  with  the  averages  of  the  25  highest  and  the  25  lowest  results  on 
the  protein  of  260  samples  of  wheat,  14.97  per  cent.,  and  9.28  per 
cent.,  respectively,  the  difference  is  5.69  per  cent,  or  48  per  cent,  of  the 
general  average  (11.95  Per  cent.).  In  other  words  the  variation  in  the 
corn  is  only  one-sixth  less  than  that  in  the  wheat.  It  may  be  noted 
that  if  we  include  the  analyses  of  sweet  corn  (all  varieties  of  wheat  are 
considered)  the  variations  in  the  protein  content  of  corn  exceed  those  in 
wheat.  Jenkins  and  Winton's  compilation2  shows  the  protein  content 
to  vary  more  in  208  samples  of  corn  than  Richardson  found  in  260 
samples  of  wheat. 

As  to  the  assumption  regarding  the  Pacific  Slope  it  may  be  pointed 
out  that  the  table  of  analyses  from  the  different  States  shows  the  average 
of  5  analyses  of  Pennsylvania  corn  to  agree  well  in  percentage  of  pro- 
tein with  the  single  analyses  from  Oregon  and  Washington.  The  aver- 
age of  12  analyses  of  corn  from  California  reported  in  1884  by  Richard- 
son3 shows  practically  the  same  percentage  of  protein  as  the  general 
average  for  the  United  States. 

In  1886  Flechig4  made   analyses   of  14  different  varieties   of  corn, 


'U.  S.  Dept.  of  Agr.,  Division  of  Chemistry  Bulletin  (1883),  1. 
2U.  S.  Dept.  Agr.,  Exp.  Station  Bulletin  (1892)  11,  100. 
3U.  S.  Dept.  Agr.,  Division  of  Chemistry  Bulletin  (1884)  4. 
••Landwirtschaftliche  Versuchs-Stationen  (1886)  32,  17. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  137 

all  grown  under   uniform   conditions  of  weather,  soil,  and  fertilization. 
If  we  omit  a  variety  of  sweet  corn1  the  following  are  his  results:'' 

Variety.  Ash.       Protein.       Oil.      Carbohyrates. 


Jaune  HStif  d'Antonina   

•  29 

12.63 

S   4O 

80  68 

Rother   Hiihnermais  

.43 

1  1  06 

S   80 

80  71 

Weisser  steirischer  

si 

10.  so 

c    32 

82  67 

Weisser  ungarischer  

.63 

q  88 

6    21 

82  28 

Canquatino  

.48 

9.88 

S    S2 

8^    12 

Tiirkischer  vierzigtiigiger   

•73 

9.69 

s.88 

82.70 

Canadischer  aus  Ungarn  

.58 

q   CQ 

6  oo 

82    Q2 

Bunter  Augustmais  

.44 

Q.  SO 

s  02 

84    O4 

Friih.  Amerik.  Bernsteinmais  

.42 

9   J9 

S  .7S 

8s  64 

Friiher   Badischer   

.46 

9.06 

S.43 

84  .OS 

Blanc  hiitif  des  Landes   

.60 

9.00 

6.22 

83.18 

Improved  King  Philip  

•54 

8.95 

S.43, 

84.08 

PaDaeeienmais.  . 

.  is 

8.60 

s.88 

84.08 

In  view  of  the  fact  that  reference  has  already  been  made  to  the 
wide  limit  of  error  in  fiber  determinations,  it  may  be  noted  here  that 
the  total  variation  on  the  final  results  for  fiber  as  reported  by  Flechig 
on  the  13  samples  of  corn  is  from  1.23  per  cent,  to  1.86  per  cent., 
while  the  variation  in  the  separate  determinations  made  on  a  single 
sample  is  from  1.26  per  cent,  to  1.83  per  cent.  It  is  also  observed  that 
Flechig's  results  indicate  protein  as  the  most  variable  constituent  of 
corn  grown  under  uniform  conditions. 

Since  the  establishment  of  the  experiment  stations  in  the  United 
States  the  number  of  proximate  analyses  of  corn  has  been  greatly 
increased*,  but  in  the  main  the  analyses  have  been  made  for  special  pur- 
poses (as  in  feeding  experiments)  other  than  a  study  of  the  corn  itself, 
and  upon  samples  whose  history  was  unknown  or  unnecessary  for  the 
object  in  view.  Only  one  series  of  these  analyses  will  be  discussed  in 
this  connection. 

^n  1893  the  Connecticut  Experiment  Station  published4  the  analyses 
of  90  samples  of  corn  grown  in  1892  in  various  parts  of  the  state  from 
about  75  differently  named  varieties,  and  under  exceedingly  varying 
conditions  of  weather,  soil,  cultivation,  fertilization,  etc.  If  we  omit 
one  sample  of  sweet  corn,  and  one  sample  which  was  injured  by  hail 
before  maturing,  the  following  are  the  five  highest  and  the  five  lowest 
results  from  all  determinations  of  each  constituent;  also  the  general 
average  of  all  analyses: 

'Sucre  ride'. 

'*A  few  errors  were  found  in  Flechig's  summary  which  I  have  corrected  from 
his  analytical  data.  Fiber  is  included  in  the  column  headed  carbohyrates. 

3Especially  by  U.  S.  Dept.  of  Agr.  and  Stations  of  Conn.,  Mass.,  111.,  Vt.  and 
N.  J. 

4Conn.  Agr.  Exp.  Station  Annual  Report  (1893). 


'38 


BULLETIN    NO.     53. 


Ash. 

ist    highest 2.10 

2nd  i  .go 

3rd       "        1.86 

4th        "        i.  80 

5th        "        1.79 

ist    lowest 91 

2nd      "        98 

3rd      "         i  .00 

4th  i  .01 

5th  i  .04 

General  average i .  39 


Protein. 

Fat. 

Carbohydrates 

M-53 

6-39 

85.93 

14.04 

5-97 

85-14 

13.86 

5-95 

85-07 

13-33 

5-95 

84.67 

13-29 

5-95 

84.63 

8-33 

3.15 

78.56 

8.69 

3-55 

78.85 

8.79 

4.21 

78.99 

8.82 

4.28 

79.26 

8.25 

4-31 

79.85 

II  .63 


5-27 


81.71 


The  compilation1  of  Jenkins  and  Winton  gives  the  average  compo- 
sition of  dent  and  flint  corn  as  follows: 


Samples. 
Dent  .................   86 

Flint  ..................   68 

General  average  ........  154 


Ash. 


Protein. 

«.S 

ii. 8 
ii. 6 


Fat. 

5-6 
5.6 
5-6 


Carbohydrates. 
81.2 
80.9 
81.1 


By  mechanical  means  the 
corn  kernel  has  been  separated 
into  four  different  parts.  These 
may  be  designated  (fig.  i2)  as 
(a)  the  coat,  or  hull,  of  the 
kernel,  (b)  the  hard  glutenous 
layer  underneath  the  hull, 
much  thicker  at  the  sides  than 
at  the  crown,  (c)  the  chit,  or 
germ,  and  (d)  the  starchy 
matter  constituting  the  chief 
body  of  the  kernel.  It  has 
never  been  found  possible  to 
make  such  a  separation  with 
even  approximate  accuracy, 
the  separation  of  the  glutenous 
layer  from  the  starchy  portion 
being  especially  difficult.  On 
this  basis  Salisbury3  gives  the 
following  percentage  composi- 
tion of  the  kernel  with  the 
proximate  composition  of  the"  different  parts  reduced  to  the  dry  basis: 

'U.  S.  Dept.  of  Agr.,  Exp.  Station  Bulletin  (1892)  11. 

2l  am  indebted   to   Director  Voorhees,  N.  J.  Agr.  Exp    Station,  for  the   use  of 
this  cut. 

3Trans.  N.  Y.  State  Agr.  Soc.  (1848)  8,  678. 


FIG.   i. 


Glutenous 

Starchy 

layer. 

portion. 

Germs. 

66.63 

18.04 

ii  .03 

•43 

.61 

14.05 

7.65 

2.74 

21-39 

2.87 

3-07 

30.26 

89.05 

93.58 

34-30 

1898.]  CHEMISTRY    OF    THE    CORN    KERNEL  139 


Hulls. 

Percent 4.30 

Ash 4 . 56 

Protein1 

Oil 

Carbohydrates2 

In  a  microscopic  study  of  the  corn  kernel  Haberlandt3  observed  that 
the  germ  contained  a  large  amount  of  oil  while-  in  the  remaining  por- 
tions of  the  kernel  no  oil  was  apparent.  Acting  upon  this  Lenz3  under- 
took an  analytical  investigation  of  these  portions.  The  germs  were 
carefully  removed  from  the  kernels  by  mechanical  means  and  the  oil  and 
protein  in  the  two  portions  determined.  His  results  on  a  sample  of 
American  white  flint  corn  are  as  follows : 

Kernels  less  germs  Germs. 

Percent 88.18  11.82 

Per  cent  Oil4 i .  57  32 . 83 

"     "     Protein4 13.09  19 .93 

Lenz  expressed  the  opinion  that  the  small  quantity  of  oil  found  in 
the  kernel  after  the  germ  had  been  removed  was  really  due  to  particles 
of  the  germ  which  had  not  been  removed  or  to  traces  of  oil  deposited 
on  the  remainder  of  the  kernel  during  the  mechanical  process  of  remov- 
ing the  germ. 

This  was  further  investigated  by  Atwater5  who  removed  the  germ 
together  with  a  considerable  portion  of  the  kernel  immediately  sur- 
rounding the  germ  in  order  to  insure  the  separation  of  all  oil  properly 
belonging  to  the  germ.  Following  are  his  results  : 

Outer  portion  Inner  portion 

free  from  germ.  including  germ. 

Percent 76.43  23.57 

Per  cent.  Oil4 i  .63 

- 

Recently  Voorhees6  and  Balland7  have  published  the  following  re- 
sults : 

Glutenous  layer 

Hulls.         and  starchy  portion.         Germs. 
5.56  84.27  10.17  Voorhees. 

12.40  74-iQ  13.50  Balland. 

'This  is  given  here  as  the  sum  of  the  zein,  albumen,  and  casein  reported  by 
Salisbury. 

2  By  difference. 

3Allgemeine  land-  und  forstwirtschaftliche  Zeitung  (1866)  257  ;  Jahresbericht 
[Hoffmann]  iiber  die  Agricultur-Chemie  (1866)  9,  106. 

4In  the  dry  matter. 

5Thesis,  Yale  College  (1869)  ;  American  Journal  of  Science  and  Arts  (1869)  [2] 
48,  352. 

eNew  Jersey  Agr.  Exp.  Station  Bulletin  (1894)  105. 

7Comptes  rendus  des  Sct'ances  (1896)  122,  1004. 


140 


BULLETIN    NO.     53. 


The   following  table  shows  the  composition1  of  the   separate   parts 


Carbohydrate 


Ash. 

Protein. 

Oil. 

Fiber. 

extract. 

1.25 

6.52 

i-57 

16.24  - 

74.42 

Voorhees. 

1.44 

8.20 

•J.33 

ii  .25 

76.78 

Balland. 

.68 

12.15 

I.-33 

-65 

84.99 

Voorhees. 

.68 

8-53 

i.  08 

.40 

89.31 

Balland. 

IO.02 

'    19-54 

26.65 

2.59 

41  .20 

Voorhees. 

7.87 

15.32 

39-85 

1.99 

34-97 

Balland. 

(dry). 


Hulls. 

Glutenous  layer  and 
starchy  portion. 

Germs. 


These  data  confirm  the  earlier  results,  showing  the  germ,  which 
constitutes  only  about  12  percent,  of  the  kernel,  to  contain  nearly  twice 
as  much  mineral  matter  and  three  or  four  times  as  much  oil  as  all  of  the 
remaining  portions  of  the  kernel.  It  is  also  rich  in  protein.  Voorhees 
states  that  the  portion  richest  in  protein  is  the  glutenous  layer. 

In  the  manufacture  of  starch  and  glucose-sugar  from  corn  these 
different  portions  of  the  kernel  are  separated  much  more  perfectly  than 
it  is  possible  to  do  by  hand  although  their  original  composition  is  some- 
what altered.  Various  methods2  have  been  employed,  but  the  following 
will  indicate  briefly  a  common  process  : 

The  corn  is  steeped  in  warm  water  containing  a  little  sulfurous  acid 
and  then  reduced  to  a  coarse  powder.  The  germs  together  with  a  part 
of  the  hulls  are  recovered  by  floating  and  separated  after  drying.  The 
material  remaining  in  the  water  in  suspension  is  passed  through  sieves 
arid  the  remainder  of  the  hulls  and  some  other  coarse  matter  can  thus  be 
separated  from  the  starch  and  the  more  finely  divided  gluten.  The 
starch  is  finally  allowed  to  settle  and  then  the  water  containing  the  larger 
part  of  the  gluten  is  run  off.  After  further  purification  the  starch  is  sold 
as  such  or  is  manufactured  into  other  products,  as  glucose-sugar.  The 
by-products,  hulls,  "gluten,"  and  germs,  separate  or  mixed,  are  sold  as 
food  stuffs,  the  larger  part  of  the  oil  usually  having  been  expressed  from 
the  germs.  The  mineral  matter  is,  of  course,  largely  removed  from 
these  products  by  the  solvent  action  of  the  water. 

The  analyses  of  corn  oil  cake  was   reported3  by  Moser  as  early  as 

1867  with  the  following  results  : 

Carbohydrate 

Ash.  Protein.  Fat.  Fiber.  extract. 

8.07  I7-I9  ^2.58  11.41  5°-75 

The  following  is  believed  to  fairly  represent  the  composition  (dry)  of 
the  several  individual  products,  not  as  usually  found  on  the  market  but 
in  their  purest  condition  : 

JAs  published  Voorhees'  results  are  evidently  given  on  the  basis  of  ash -free 
organic  matter.  They  are  here  calculated  to  the  basis  of  total  dry  matter. 

2Journal  Society  Chemical  Industry  (1887)  6,  84. 

3Jahresbericht  (Hoffmann)  iiber  die  Agricultur-Chemie  (1867)  10,  259.  Cf.  ibid. 
(1872)  15,  21  ;  (1874)  17,  15  ;  (1876)  19,  15. 


}.]  CHEMISTRY  OK  THE  CORN  KERNEL.  141 

Carbohydrate 


Hulls'  

Ash. 
.  .  .  .   i  .  02 

Protein, 
ii.  18 

Fat. 
4-  X3 

Fiber. 
11.98 

extract. 

71  .60 

Gluten2    

.  .  1  .  14 

44  .03 

7.60 

2    26 

44   88 

Germ  cake1 

..2.  "58 

27.2^ 

M.  84 

7.41 

47  .  Q4 

Starch3  .  . 

.  .O.  ^0 

QQ.704 

The  correctness  of  Voorhees'  statement  that  the  portion  of  the  corn 
kernel  richest  in  protein  is  the  glutenous  layer  is  plainly  apparent. 

Richards5  has  recently  made  proximate  analyses  to  determine  the 
heating  value  of  the  corn  kernel.  Calorimetric  determinations  were  also 
made,  being  reported  in  terms  of  the  British  thermal  unit6.  Following 
are  the  results  : 

Volatile  Fixed  Fuel 

Moisture.         matter.  carbon.  Ash.  value. 

Yellow  dent 8.45  78.10  12.18  1.27         8202. 

White  dent 8.88  77.22  12.90  i.oo          8338. 

EXPERIMENTAL. 

Ih  the  following  work  on  the  proximate  composition  of  corn  the 
total  dry  matter,  the  ash,  the  nitrogen,  and  the  fat  were  determined 
directly.  The  protein  was  estimated  by  multiplying  the  total  nitrogen 
by  6.25  and  the  carbohydrates  by  subtracting  the  sum  of  the  ash,  pro- 
tein, and  fat  from  the  total  dry  matter.  In  each  single  determination 
of  the  several  constituents  2  gms.  of  air-dry  substance  were  regularly 
taken. 

PREPARATION  OF  SAMPLE. — All  samples  were  air-dried,  ground  to 
pass  through  a  sieve  with  circular  perforations  i  millimeter  in  diameter, 
and  then  preserved  in  air-tight  vessels,  being  thoroughly  mixed  just 
before  being  analyzed. 

DETERMINATION  OF  DRY  MATTER. — The  air-dry  substance  was  placed 
in  a  glass  tube  10  cm.  long  and  2  cm.  in  diameter  over  one  end  of  which 
a  piece  of  hardened  filter  paper  had  been  firmly  tied  with  nickel  wire, 
the  tube  with  paper  bottom  having  been  dried  and  weighed  in  weighing 
tubes  before  being  charged  with  the  substance.  The  substance  was 
dried  with  the  tube  lying  in  a  horizontal  position  in  a  current  of  dry 
hydrogen  at  a  temperature  of  105°,  maintained  by  a  boiling  aqueous 
solution  of  glycerol  in  a  double-wall  bath  provided  with  a  return  con- 
denser. The  gas  entered  the  bath  at  one  end  near  the  top  and  passed 
out  at  the  bottom  near  the  opposite  end. 

'N.  J.  Agr.  Exp.. Station  Bui.  (1894)  105. 

2Conn.  Agr.  Exp.  Station  Report  (1895)231. 

3Journal  Society  Chemical  Industry  (1887)  6,  84. 

"Starch. 

5U.  S.  Dept.  of  Agr.,  Exp.  Station  Bulletin  (1898)49,  95. 

"Heat  required  to  raise  one  pound  of  water  from  50°  to  51°  F. 


142 


BULLETIN    NO.     53. 


To  determine  the  error  in  obtaining  the  weight  of  the  empty  tubes 
with  the  paper  bottoms,  10  tubes  were  dried  for  one  hour,  cooled  in 
desiccators  and  weighed  in  weighing  tubes,  then  dried  again  for  two 
hours  and  again  weighed,  with  the  following  results  : 

First  weight.  Second  weight. 


i 47-7552 

2 49-0332 

3 46.1074 

4 48 . 9842 

5 48.6642 

6 45-4501 

7 48-546i 

8 47.8516 

9 44-8934 

10 46.2726 


47-7550 
49.0328 
46. 1074 
48.9843 
48.6641 
45.4500 

48.5455 
47.8518 
44.8930 


Decrease. 
.0002 
.0004 
.0000 

— .0001 
.0001 
.0001 
.0006 

— .0002 
.0004 

— .0001 


46.2727 

To  determine  the  length  of  time  required  under  the  conditions 
mentioned  to  reduce  the  substance  practically  to  a  constant  weight  the 
following  data  were  obtained,  2  gms.  of  air-dry  substance  being  taken 
from  12  different  samples  : 


Weight  of  substance  after  drying 


4  hours. 


Difference  in  weight 
between  drying 


4  or  8 

8  or  16 

hours. 

hours. 

.0120 

.0039 

.•0117 

•0033 

.0115 

.0041 

.0113 

.0036 

.0112 

.0037 

.0115 

.0037 

.0113 

.0041 

.OIIO 

.0038 

.0113 

.0045 

.0114 

-0035 

.0118 

.0048 

.0106 

.0039 

16  hours. 
1.7600 
.7512 

•7413 
.7489 

.7513 
.7483 
•7435 
.7503 

I .7387 

1-7457 
1.7411 

After  drying  4  hours  the  average  decrease  in  weight  for  four  hours 
more  is  0.0114  gms.  or  0.6  per  cent,  of  the  amount  determined,  and 
then  for  8  hours  more  it  is  0.0039  Sms-  or  °-2  Per  cent,  of  the  amount 
determined.  This  is  a  much  narrower  limit  of  error  than  can  be  main- 
tained in  the  determination  of  the  constituent  groups  of  the  dry  matter, 
and  all  dry  matter  determinations  which  follow  were  made  by  drying 
the  substance  8  hours.  It  is  noteworthy  that  during  the  second  and 
third  periods  of  drying  all  of  the  samples  lost  weight  and  in  very  nearly 
equal  amounts,  showing  that  for  comparative  results  a  very  high  degree 
of  accuracy  is  attained. 

The  following  work  was  done  to  test  the  agreement  of  duplicate 
determinations  on  the  same  sample.  Twelve  different  samples  were 
selected,  and  the  24  portions  of  2  gms.  each  were  all  dried  together: 


i898.] 


CHEMISTRY    OF    THE    CORN    KERNEL. 


Weight 

of  dry 

matter. 

Variation. 

i  .  . 

.  .  1.8276 

1.8273 

.0003 

2  .  . 

.  .  i  .8230 

1.8238 

.0008 

3-- 

..1.8218 

i  .8222 

.0004 

4-- 

..1.8319 

1.8314 

.0005 

5-- 

.  .  i  .8244 

i  .8249 

.0005 

6.. 

..1.8198 

i  .8194 

.0004 

7-- 

.  .1.8264 

1.8267 

.0003 

Weight  of  dry 
matter. 


. i .8240 
.1.8243 
. i .8202 
.1.8176 
. 1.8150 


i  8242 
i .8240 
i . 8209 
i. 8186 
1-8155 


Variation. 
.0002 
.0003 
.0007 
.0010 
.0005 


Average 0005 

From  these  results  and  those  preceding  it  is  seen  that  determina- 
tions made  in  the  same  bath  and  at  the  same  time  show  a  remarkable 
degree  of  accuracy  when  compared  only  with  themselves,  and  among 
themselves  they  are  strictly  comparable. 

To  determine  the  variation  which  might  be  caused  by  unavoidable 
differences  in  temperature,  hydrogen  current,  etc.,  the  following  36 
duplicate  determinations  of  dry  matter  were  made,  in  every  case  the 
duplicate  determinations  being  made  at  different  times,  /.  <?.,  the  first 
determination  on  each  sample  was  made  one  or  more  days  previous  to 
the  second,  or  duplicate,  determination: 


Weight 

of  dry 

Weight  of 

dry 

matter.            Variation. 

matter 

Variation. 

i  .  . 

..1.7456 

1.7489 

•0033 

2O.  . 

.  .    1.7566 

1.7520 

.0046 

2.  . 

..1-7493 

L7527 

.0034 

21  . 

...1.7730 

1.7719 

.0011 

3-. 

..1.7444 

1.7441 

.0003 

22  . 

...1-7795 

1-7734 

.0061 

4-- 

..1.7362 

1.7360 

.OOO2 

23- 

...1.7668 

J-7593 

.0075 

5-. 

.  .  i  .7200 

1.7238 

.0038 

24. 

...1.7584 

1.7502 

.0082 

6.. 

••1-7514 

i-754i 

.OO27 

25, 

...1.7560 

1-7534 

.0026 

7-. 

..1.7675 

1.7689 

.0014 

26.. 

•    I-743I 

r-7435 

.0004 

8.. 

.  .1.7628 

1.7637 

.OOO9 

27     , 

..1.7526 

!-754Q 

.0014 

9-. 

..i.  7659 

1-7673 

.OOI4 

28. 

...1.7540 

1-7539 

.0001 

10.  . 

..1.7540 

1.7588 

.0048 

29., 

..1.7590 

1-7599 

.0009 

ii  .. 

..1.7522 

1-7547 

.OO25 

30. 

.  .  ,1.7494 

1.7512 

.0018 

12  .. 

-.1-7554 

1-7592 

.0038 

31     • 

..1.7489 

1-7465 

.0024 

I3-. 

.  .  i  .  7698 

1-7739 

.0041 

32., 

.  .  i  .  7498 

1-7497 

.0001 

14.. 

..1.7546 

1-7586 

.0040 

33-. 

••1.7552 

1-7559 

.0007 

I5-. 

..i  7691 

1.7741 

.O05O 

34- 

...1.7925 

1.7928 

.0003 

16.. 

..1.7552 

1-7573 

.OO2I 

35- 

...1.7515 

1.7481 

.0034 

17.. 

iS 

...1.7723 

1.7689 

.0034 

36 

.  .    I-7451 

i  .7408 

-0043 

I  o  .  . 
IO. 

•  •  I-7736 
.  .  i  .  7760 

i  .  7096 

I  .T7A2 

.  0040 
.OOl8 

Average 

.0027 

The  maximum  variation  0.0082  is  0.5  per  cent,  of  the  average 
amount  determined;  and  is  very  much  greater  than  when  the  duplicates 
were  made  at  the  same  time.  However,  the  agreement  still  appears 
very  satisfactory.  In  all  subsequent  work  herein  reported  the  duplicate 
determinations  of  dry  matter  were  made  at  different  times  in  order  that 
the  results  may  show  the  widest  variations  possible  with  the  method 
employed. 

DETERMINATION  OF  ASH. — The  air-dry  substance  was   placed  in  a 


144  BULLETIN    NO.     53. 

porcelain  crucible  and  burned  to  constant  weight  in  a  muffle  at  a  low  red 
heat,  at  a  temperature  below  that  at  which  portions  of  the  ash  would 
become  fused  and  attached  to  the  crucible. 

DETERMINATION  OF  NITROGEN. — This  was  made  by  the  ordinary  Kjel- 
dahl  method.  The  metallic  mercury  used  in  the  digestion  was  measured 
in  a  capillary  tube,  one  end  of  which  is  doubly  bent  so  as  to  form  a 
loop,  the  short  arm  of  which  is  turned  back  upon  itself  near  the  end 
while  the  long  arm  serves  as  a  handle.  The  loop  is  made  sufficiently 
narrow  to  pass  into  the  mercury  bottle,  and  of  sufficient  length  to  retain 
when  raised  above  the  liquid  the  exact  quantity  of  mercury  required  for 
a  single  determination.  By  blowing  in  the  longer  arm  the  mercury  is 
emptied  into  the  digestion  flask. 

Heavy  copper  flasks  were  used  in  the  distillation  with  much  satis- 
faction, the  sodium  hydroxid  solution  (containing  the  necessary  amount 
of  potassium  sulfid)  being  added  in  sufficient  excess  to  "bump"  before 
the  contents  may  become  dry,  thus  serving  as  a  signal  that  the  distilla- 
tion has  gone  far  enough. 

Two  common  sources  of  error  in  the  nitrogen  determination  were 
found  and  investigated.  In  titrating  an  acid  solution  in  an  open  vessel 
with  standard  ammonia  solution  a  very  appreciable  error  is  introduced 
by  the  volatility1  of  the  ammonia,  although  the  only  possible  loss  is 
from  the  tip  of  the  burette  and  from  the  falling  drops. 

In  the  following  work  ammonia  of  about  one-sixth  normal  strength 
was  used,  the  hydrochloric  acid  being  of  such  strength  that  3  cc.  were 
equivalent  to  approximately  4  cc.  of  ammonia.  The  hydrochloric 
acid  was  measured  from  an  automatic  overflow  pipette  of  15  cc.  capac- 
ity, and  the  'ammonia  from  an  automatic  overflow  burette  graduated  to 
0.05  cc.  and  drawn  to  a  fine  tip  at  the  outlet.  The  pipette  and  burette 
were  each  provided  with  three  way  stopcocks  through  which  the 
standard  solutions  were  drawn  from  the  stock  bottles  by  means  of 
syphons.  Perfectly  neutral  water  free  from  ammonia  and  carbon  dioxid 
was  used  for  diluting.  Lacmoid  served  as  the  indicator  and  gave  an 
exceedingly  sharp  end  reaction. 

By  titrating  in  beaker  flasks  with  the  tip  of  the  ammonia  burette 
well  below  the  top  of  the  flask  the  following  results  were  obtained,  the 
length  of  time  taken  in  making  the  titration  being  also  given: 

i 15  cc.  HC1  required  20. 10  cc.   NH3, — time  =  i   minute. 

2 15  cc.  HC1         "         20.08  cc.  NH3, —    "     =  i         " 

3 15  cc.  HC1         "         2o.i2cc.  NH3, —    "     =  i         " 

4 15  cc.  HC1         "          20.3OCC.   NH3,—     "     =  2 

5 15  cc.  HC1         "         20.25CC.   NH3, —    "     =  2 

6 15  cc.  HC1          "          20.4OCC.   NH3, —     "     =  3 

tRempel  has  already  shown  that  dilute  ammonia  solution  drawn  into  beakers  or 
evaporating  dishes  and  then  titrated  suffers  marked  loss. — Zeitschrift  f iir  angewandte 
Chemie  (1889)  331, 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  145 

By  titrating  in  an  Erlenmeyer  flask  attached  to  the  burette  by  means 
of  a  rubber  stopper1,  provided  with  a  capillary  tube  for  relieving  the 
pressure,  the  following  results  were  obtained  : 

i 15  cc.  HC1  required  19.82  cc.   NH3, — time  =  i  minute. 

2 15  cc.  HC1        "        19.83  cc.  NH3,—    "      =i 

3 15  cc.  HC1        "        19.81  cc.  NH3,—    "      =3 

4   15  cc.  HC1        "        19.81  cc.  NH3,—    "      =  5 

As  from  3  to  5  minutes  are  taken  to  make  a  titration  when  the 
amount  of  ammonia  required  is  not  known,  as  in  ordinary  nitrogen  de- 
terminations, the  error2  from  titrating  in  open  vessels  becomes  an  im- 
portant factor,  the  total  variation  in  the  two  series  of  experiments  above 
noted  amounting  to  0.6  cc.  or  3  per  cent,  of  the  ammonia  required.  The 
fact  that  the  density  of  ammonia  gas  is  but  little  more  than  half  that  of 
air  explains  its  rapid  upward  diffusion  from  an  open  vessel. 

Another  error  in  nitrogen  determinations  may  occur  in  the  distilla- 
tion by  loss  of  ammonia  from  the  receiving  flask  in  case  there  is  not 
sufficient  acid  above  the  end  of  the  delivery  tube  to  neutralize  all  of  the 
ammonia  distilled  over. 

In  the  following  work  a  quantity  of  a  very  dilute  solution  of  am- 
monium chlorid  was  prepared  by  exactly  neutralizing  standard  hydro- 
chloric acid  with  standard  ammonia  and  diluting  with  ammonia-free 
water.  A  quantity  of  this  solution  equivalent  to  12  cc.  of  standard  am- 
monia was  placed  in  a  distillation  flask  with  an  excess  of  sodium 
hydroxid  and  distilled  into  iscc.  of  standard  hydrochloric  acid  diluted 
to  about  40  cc.,  the  end  of  the  delivery  tube  from  the  condenser  dipping 
well  into  the  acid  solution.  The  relation  of  the  standard  acid  and  am- 
monia solutions  was  such  that  15  cc.  HC1  were  equivalent  to  19.82  cc. 
NH3.  Six  distillations  were  made,  in  each  case  ammonium  chlorid 
equivalent  to  i2cc.  of  standard  ammonia  solution  being  taken.  Fol- 
lowing are  the  amounts  of  standard  ammonia  solution  required  to 
neutralize  the  excess  of  acid  : 

Required. 

i 8.20  cc. 

2   7-85  cc. 

3 7-93  cc. 

4 8.60  cc. 

5 7-84  cc. 

6 7-95  cc. 

Two  of  these  are  practically  exact,  the  other  four  showing  errors 
varying  from  o.  1 1  cc.  to  0.78  cc.  of  standard  ammonia. 

This  work  was  repeated  with  the  distillation  from  quantities  of  am- 
monium chlorid  equivalent  to  15  cc.  of  standard  ammonia  solution,  the 

1By  using  a  stopper  which  has  been  bored  nearly  through  from  the  small  end 
by  a  large  borer,  the  flask  may  easily  be  given  a  free  rotary  motion. 

2Confirmed  by  recent  (unpublished)  work  of  Dr.  F.  L.  Kortright. 


Calculated. 

Error. 

7.82  cc. 

0.38  cc. 

7.82  cc. 

0.03  cc. 

7.82  cc. 

O.I  I  CC. 

7.82  cc. 

0.78  cc. 

7.82  cc. 

O.O2  CC. 

7.82  cc. 

0.13  cc. 

146  BULLETIN    NO.     53. 

other  conditions  being  as  before.      Following  are  the  amounts  of  stand- 
ard ammonia  solution  required  to  neutralize  the  excess  of  acid  : 

Required.  Calculated.  Error. 

i 6 . 10  cc.  4 . 82  cc.  i .  28  cc. 

2 5.4000.  4.82  cc.  o.58cc. 

3 5-95CC.  4.82CC.  1.130;. 

4 6.2OCC.  4.82  cc.  1.380:. 

5 5.65  cc.  4.82  cc.  0.83  cc. 

6 5.i8cc.  4.82  cc.  0.360;. 

Diluting  the  residues  in  the  distillation  flasks  with  ammonia-free 
water,  and  distilling,  gave  no  further  addition  of  ammonia  in  any  case. 

It  was  observed  that  in  both  trials  the  greatest  errors  occurred  with 
Nos.  i  and  4.  A  careful  inspection  of  the  apparatus  showed  all  con- 
nections to  be  perfect.  It  was  observed,  however,  that  the  delivery 
tubes  from  Nos.  i  and  4  did  not  reach  as  far  into  the  acid  solution  as 
most  of  the  others. 

With  the  thought  that  possibly  ammonia  escaped  from  the  receiving 
flasks,  the  following  six  distillations  were  made,  in  each  the  quantity  of 
ammonium  chlorid  employed  being  equivalent  to  19.32  cc.  of  standard 
ammonia  solution;  thus,  exactly  o.  50  cc.  of  standard  ammonia  should 
have  been  required  to  neutralize  the  excess  of  acid.  Some  lacmoid  in- 
dicator was  added  to  the  acid  solutions  in  receiving  flasks  Nos.  i,  3, 
and  5;  strips  of  moistened  red  litmus  paper  were  also  hung  in  the  necks 
of  these  flasks.  During  the  process  of  distillation,  receiving  flasks  2,  4, 
and  6  were  agitated  to  keep  their  contents  thoroughly  mixed. 

It  was  observed  that,  during  the  process  of  distillation,  in  receiv- 
ing flasks  i,  3,  and  5  the  liquid  above  the  end  of  the  delivery  tube  turned 
blue,  while  a  layer  of  liquid  below  this  remained  red;  also  that  the 
moistened  red  litmus  paper  hung  in  the  necks  of  these  flasks  turned 
blue. 

In  titrating  the  excess  of  acid  the  amounts  of  standard  ammonia 
required  were  as  follows  :  -*. 

Required.  Calculated.  Error. 

I 2.6OCC.  O.fOCC.  2.IOCC, 

2 O.5OCC.  O-5OCC.  O.OO  CC. 

3...    ....2.2ycc.  0.50CC.  i.yycc. 

4 0.53  cc.  0.50CC.  0.03  cc. 

5 i .  99  cc.  o .  50  cc.  i .  49  cc. 

6 o .  50  cc.  o .  50  cc.  o .  oo  cc. 

The  explanation  for  the  separation  of  the  liquid  in  the  receiving 
flasks  into  two  layers  as  described  is  to  be  found  in  the  different 
densities  of  aqueous  solutions  of  ammonia  and  hydrochloric  acid. 

In  subsequent  work  I  have  used  delivery  tubes  reaching  to  the  very 
bottom  of  the  receiving  flasks,  and  contracted  at  the  end  to  an  aperture 
of  but  4  or  5  mm.  diameter.  This  insures  considerable  agitation  of  the 


i898.] 


CHEMISTRY    OF    THE    CORN    KERNEL. 


content  of  the  receiving  flask  produced  by  irregularities  in   the  boiling 
of  the  liquid  in  the  distillation  flask. 

This  loss  of  ammonia  shown  to  have  taken  place  from  the  very 
dilute  solution  in  the  receiving  flask  after  cooling  by  an  efficient  con- 
denser emphasizes  the  results  of  the  preceding  work  on  titration  and 
the  importance  of  avoiding  a  common  error  in  that  process. 

DETERMINATION  OF  FAT. — The  glass  tube  with  the  bottom  of  hardened 
filter  paper  (previously  described)  containing  the  dry  matter  from  2  gms. 
of  air-dry  substance  was  placed  in  a  Soxhlet  tube  and  the  fat  extracted, 
the  solvent  passing  through  the  substance  and  being  filtered  by  the  paper 
bottom.  This  arrangement  is  for  several  reasons  preferred  to  the  use 
of  tubes  made  entirely  of  filter  paper,  i.  The  determination  of  dry 
matter  and  the  extraction  of  fat  are  done  in  the  same  tube  without 
transferring  the  substance.  2.  The  solvent  must  pass  through  the  sub- 
stance. 3.  The  hardened  paper  can  be  removed  from  the  tube  (after 
taking  off  the  wire  ligature),  spread  out  in  the  side  of  a  funnel  and  the 
fat-free  substance  easily  and  completely  removed  from  both  paper  and 
tube,  by  washing  with  the  hot  dilute  sulfuric  acid  to  be  used  in  case  a 
fiber  determination  is  desired. 

The  ether  used  in  the  extraction  was  kept  over  metallic  sodium  in 
the  form  of  wire,  and  redistilled  before  being  used.  The  upper  end  of 
the  condenser  was  protected  by  a  calcium  chlorid  tube. 

Mainly  to  avoid  the  constant  trouble  of  having 
atmospheric  moisture  condense  upon  the  outer  sur- 
face of  a  Liebig  or  Allihn  condenser  and  run  down 
over  the  extraction  apparatus,  the  following  form 
of  condenser  (fig.  2)  was  designed  : 

This  condenser  is  made  entirely  of  glass,  and 
consists  of  a  thin  glass  tube  (a)  25  mm.  outside 
diameter  and  25  cm.  long,  provided  with  two  glass 
tubes  about  6  mm.  in  diameter,  one  reaching  to 
near  the  bottom  of  (a),  sealed  in  for  water  inlet 
and  outlet.  The  tube  (a)  is.  surrounded  by  a 
stronger  glass  tube  (b)  of  30  mm.  inside  diameter 
sealed  on  at  the  top  and  narrowed  at  the  lower 
end  to  a  10  mm.  tube  which  extends  8  mm.  below 
and  is  ground  off  obliquely  at  the  end.  About  3 
cm.  from  the  top  of  tube  (b)  a  side  tube  (c)  is 
provided;  it  is  5  cm.  long  and  12  mm.  inner 
diameter,  and  is  widened,  as  indicated  in  the 
Pig  2  figure,  where  it  is  sealed  into  (b).  The  water 

tubes  are  cut  off  at  a  length-of  5  cm.,  being  blown  as  indicated  to  hold 
a  rubber  tube. 

The  outer  tube  of  this- condenser  is  not  cooled  to  a  temperature  at 


148  BULLETIN    NO.     53. 

which  atmospheric  moisture  will  condense  upon  it.  This  is  its  chief 
advantage  over  the  ordinary  form  in  fat  extraction  with  anhydrous 
ether.  The  side  tube  serves  to  connect  with  a  drying  tube.1 

In  making  the  proximate  analyses  which  are  reported  herein  the  fat 
was  always  heated  in  a  current  of  dry  hydrogen  for  3  hours  at  105°; 
the  flask  allowed  to  cool  in  the  air  and  then  to  stand  in  the  balance  case 
until  the  weight  became  constant.  The  flasks  used  in  the  work  were  of 
Erlenmeyer's  pattern  with  about  100  cc.  capacity  and  weighed  25  to  30 
gms.  each.  Differences  of  barometric  pressure  and  of  humidity  of  the 
atmosphere  of  the  laboratory  may  easily  produce  slight  changes  in 
weight. 

To  cool  the  flasks  in  desiccators  before  weighing  was  found  unsatis- 
factory on  account  of  the  fact  that  the  perfectly  dry  air  of  the  desic- 
cator is  considerably  heavier  than  the  moist  air  of  the  laboratory,  and 
after  the  flask  is  removed  from  the  desiccator  its  weight  does  not  become 
constant  until  the  dry  air  is  replaced  by  that  of  the  laboratory  and  the 
condensation  of  moisture  upon  the  surface  of  the  glass  ceases. 

In  all  of  my  analyses  herein  reported  to  determine  the  proximate 
composition  of  corn,  two  complete  single  analyses  were  made;  the 
computations  were  made  separately  with  no  averages,  and  the  results 
are  reported  separately.  Furthermore  the  two  analyses  were  made  at 
different  times,  and  the  differences  between  the  duplicates  certainly 
fairly  represent  the  experimental  error.  The  computations  were  made 
by  logarithms  and  directly  to  the  percentage  composition  of  the  dry  matter 
The  logarithm  of  6.25  was  included  in  the  proper  factor  logarithm  for 
calculating  the  protein  equivalent  from  cubic  centimeters  of  standard 
ammonia  solution.  In  no  case  has  the  percentage  of  nitrogen  or  the 
percentage  composition  of  the  air-dry  substance  been  calculated.  If 
desired  the  former  can  be  determined  exactly  by  dividing  the  percentage 

1A.  few  other  important  points  may  be  noted.  The  condenser  may  be  used  in 
ordinary  distillation  by  passing  the  vapor  in  through  the  side  tube.  The  ordinary- 
condenser  frequently  breaks  in  consequence  of  the  extreme  differences  in  the  temper- 
ature of  the  inner  tube  just  above  and  below  the  surface  of  the  surrounding  water. 
The  new  form  is  free  from  this  objection.  The  water  tubes  are  both  at  the  top  and 
very  convenient  for  joining  up  a  series  of  condensers.  These  condensers  are  more 
compact  and  yet  much  more  effective  than  the  ordinary  form,  the  vapor  being  dis- 
tributed in  a  thin  layer  over  a  very  large  condensing  surface,  the  outer  tube  also 
acting  as  an  "air  condenser." 

These  condensers  have  been  in  almost  constant  use  during  the  past  year  in  the 
chemical  laboratories  of  the  University  of  Illinois  and  have  given  excellent  satis- 
faction. 

There  are  several  condensers  which  have  the  water  tube  inside,  but  I  have 
found  none  suited  to  the  purpose  for  which  this  was  especially  designed  except  that 
recently  described  by  Sudborough  and  Feilmann  (Jour.  Soc.  Chem.  Ind.  (1897)  16, 
979),  which  is  certainly  to  be  preferred  to  the  ordinary  form  as  a  return  condenser, 
•though  it  cannot  be  used  safely  in  distillation. 


1898.  I  CHEMISTRY  OF  THE  CORN  KERNEL.  149 

of  protein  by  6.25.  The  fact  that  the  moisture  content  of  air-dry  corn 
merely  depends  upon  the  weather  and  is  just  as  changeable  is  deemed 
sufficient  reason  for  ignoring  the  percentage  composition  of  the  air-dry 
substance  in  this  study. 

COLLECTING  SAMPLES  OF  CORN. — To  determine  the  accuracy  of  taking 
samples  of  corn  a  bushel  or  more  of  shelled  corn  from  each  of  ten 
different  lots  was  thoroughly  mixed,  and  then  two  samples  of  one  pint 
each  were  taken  for  analysis,  a  single  analysis  being  made  of  each 
sample.  Following  are  the  results  obtained: 

Carbohy-  Carbohy- 

Ash.       Protein.      Fat.        drates.  Ash.  Protein.  Fat.       drates. 

j j  1.42         10.07         4-71         83.80  ,11.48  11.04  4-66        82.82 

I  i. 42         10.19        4-73         83.66  (  1.45  10.81  4.63         83.11 

2ji.4i          10.85         4-43         83.31  7JI-5°         "-33         4-79         82.38 

(  1.41         10.78         4.40        83.41  I  i-49         n-43         4-77         82.31 

j  1.43         10.72         4.24         83.61  g(  1.51         11.35         5.14         82.00 

3  /  i . 43         10.66         4.25         83.66  1  1.54         11.42         5.15         81.89 

1.50         11.40         4.44         82.66  (1.43         1 1. 1 1         4.76         82.70 

1.53         11.42         4.49         82.56  9|i.43         11.09         4-8i         82.67 

I  1.48         11.24         4-73         82.55  I  *-49         11.09         4-73         82.69 

^  {  i  47         11.04         4-73         82.76  °  |  1.48         1 1. 02         4.73         82.77 

These  results  show  the  method  of  sampling  to  be  satisfactory.  The 
variations  between  results  on  duplicate  samples  are  scarcely  greater  than 
the  experimental  error  in  making  duplicate  analyses  of  a  single  sample1, 
although  variations  among  the  different  lots  amount  to  very  much  more. 
This  is  especially  marked  in  the  fat  column  where,  although  the  average 
amount  determined  is  less  than  5  per  cent.,  there  is  a  difference  among 
the  lots  of  from  4.25  to  5.15  or  0.90  per  cent,  and  between  duplicate 
samples  of  only  0.05  per  cent. 

ANALYSES  OF  ONE  VARIETY.2 — The  following  ten  duplicate  analyses 
were  made  to  determine  the  possible  variation  in  a  single  variety  of  corn 
which  had  been  grown  under  conditions  as  nearly  uniform  as  possible. 
From  each  of  ten  different  tenth-acre  plots  lying  in  the  same  field  several 
bushels  of  corn  were  taken.  The  corn  was  shelled,  thoroughly  mixed, 
and  a  pint  sample  taken  from  each  lot  for  anaylsis.  Following  are  the 

results  obtained: 

Carbohy-  Carbohy- 

Ash.       Protein.       Fat.        drates.  Ash.       Protein.       Fat.        drates. 

\  1.39         11.24         4-43         82.94  j  *-33         11.19        4.27        83.21 

<  1.41          11.17         4-41         83.01  |  1.36         11.08         4.27         83.29 

.42         11-54         4-45         82.59  j  1.49         11.47         4-38         82.66 

.43          11.50         4-47          82.60  ^  |  I   50          11.41          4.30         82.79 


'See  the  following  table. 

2  A  variety  of  white  dent  corn  well  known  in  Illinois  as  Burr's  White.  This 
corn  has  been  grown  in  large  quantities  for  several  years  upon  the- University  of  Illi- 
nois Agricultural  Experiment  Station  fields,  and  special  precautions  have  been  taken 
to  keep  it  pure  and  distinct. 


«5°                                                              BULLETIN  NO.     53.                                                        [July, 

Carbohy-  Carbohy- 

Ash.       Protein.       Fat.        drates.  Ash.  Protein.  Fat.        drates. 

(1.34         11.26        4.49        82.91  0(1.42  11.49  4.26        82.83 

5}i.34         11.24         4.47         82.95  (  1-41  n-44  4-30         82.85 

, j  1.38         11.62         4.44         82.56  (  1.39  11.56  4-47         82.58 

I  1.42         11.70        4.41         82.47  |  *. 39  "-5i  4-55         82.55 

j  1.41         11.42         4.36         82.81  \  1.42  H-47  4-42         82.69 

'|i.38         11.33         4-39         82.90  E    (  1.43  11.45  4.48         82.65 

These    results    show  a  marked  degree    of  uniformity,    seen    more 

clearly  from  the  following  maxima  and  minima  of  all  determinations: 

Ash.  Protein.  Fat.  Carbohydrates. 

Maximum 1.50  11.70  4-55                83.29 

Minimum 1.33  11.08  4.26                82.47 


Difference 0.17  0.62  0.29  0.82 

By  referring  to  Flechig's  experiment  (page  137)  it  is  seen  that  with 
thirteen  different  varieties  of  corn  grown  under  uniform  conditions  he 
obtained  results  showing  the  following  variations  : 

Ash.  Protein.  Fat.  Carbohydrates. 

Maximum-. 1.73  12.63  6.22  84.08 

Minimum ...1.29  9.00  5.02  80.68 

Difference.... 0.44  4.63  1.20  3.40 

ANALYSES  OF  DIFFERENT  EARS. — In  order  to  investigate  more  fully 
the  question  of  variation  or  uniformity  in  a  single  variety  50  separate  ears 
of  Burr's  White  corn  from  the  same  field  as  that  used  in  the  preceding 
experiment  were  carefully  selected  from  a  number  of  bushels  which  had 
been  especially  picked  out  for  seed  corn.  The  50  ears  were  all  well 
formed  and  well  matured,  and  had  been  grown  in  a  field  which  had  been 
selected  because  of  its  uniform  soil  conditions.  Duplicate  analyses  were 
made  of  the  corn  from  each  ear.  Following  are  the  results  obtained  : 

Carbohy-  Carbohy- 

Ash.       Protein.       Fat.         drates.  Ash.  Protein.  Fat-         drates. 

1.44         10.79        5.66         82.11  gti.n           8.41  4.86        85.62 

1.46         10.86         5.65         82.03  I  1. 10           8.35  4.90         85.65 

.60         12.77         5-!9         80.44  I  1.41  9.91         4.22         84.46 

.60         12.84         5.22         80.34  I  *»4*         10.00         4.24         84.34 

1.32         10.77      "  4-i6         83.75  j  L44         11.46         5.01         82.09 

1.29         10.76         4.11         83.84  [     |  1.43         11-35         5.02         82.20 

j  1.36         10.49         4.53         83.72  nJI-54         12.4°         4-6i         81.45 

4  { 1.26  10.46  4.54  83.74   i. i  •  56  12.36  4.62  81.46 

j  1.09  9.33         4.35         85.23  I2Ji-39  9-99         4-41         84-2i 

•*  I  1. 10  9.27         4.41         85.22  /J-38  9.96         4.42         84.24 

,ji.34  9. ii         4.06         85.49  T,^!-37         10.12         4-8o         83.71 

j  1.32  9.13         4.13         85.42  J}i.36         10.05         4-85         83.74 

\  1.30         10.41         4.19         84.10  (  1.36         10.31         5.24         83.09 

'fx.aS        10.41        4.15        84.16         I4|i.36        10.31        5.26       83.07 


ji 
\  i 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  151 


Ash. 

Protein. 

Fat. 

Carbohy- 
drates. 

Ash. 

Protein. 

Fat. 

Carbohy 
drates. 

15  i  1^33 

9.70 
9.65 

4.01 
4.01 

84.95 
85.01 

H 

1.16 

1.17 

9.01 
9  13 

4.04 
4.06 

85.79 
85.64 

I6I':« 

11.88 
11.86 

4.62 
4.60 

82.05 
82.10 

H 

1.50 
1.52 

12.72 
12.86 

4.24 
4.26 

8L54 
81.36 

17  i.1:  " 

10.79 
10.67 

4-52 
4-54 

83.34 
83.45 

H 

1-45 
i  .46 

11.83. 

4  93 
4-93 

Si.79 

81.88 

I8|::5o 

13.88 
13-85 

5-71 
5-73 

78.93 
78.92 

H 

1.48 
1.50 

12.07 
12.06 

4.60 
4.62 

81.85 
81.82 

"i::!i 

"•55 

11.52 

4-33 
4.29 

82.69 
82.76 

37  | 

1.58 
i.  60 

12.35 
12.44 

4.76 

81.31 
81.24 

H::f3 

ii  .63 
ii  .64 

4.56 
4-57 

82.49 
82.46 

38  j 

i-33 
1-36 

9.38 
9.06 

4.86 
4.82 

84.43 
84.76 

«.\%. 

.  i  i  .  30 
ii.  19 

4-15 
4.17 

83.19 
83-27 

H 

i  .62 
i.  60 

10.72 
10.71 

4.69 
4-71 

82.97 
82.98 

22  1  i-34 

ii.  Si 
ii  .91 

4-97 
5-03 

81.87 
81.72 

4o  | 

1-54 
1-55 

9-85 
9-95 

4-95 

4-99 

83.66 
83-51 

j  1.40 
j  1  1.40 

IO.22 

10.  13 

6.  02 

6.02 

82.36 

82.45 

H 

1-55 
1-57 

10.69 
10.67 

4.92 
4.90 

82.84 
82.86 

|  1.48 
"^  {  i  .46 

II  .  14 

II.  16 

5-15 

82.27 
82.23 

H 

L47 

12.98 
12.94 

3.98 
3-95 

8i.57 
81.66 

25  -I1"61 
D  1  1-59 

II  .46 
11.38 

5-19 
5.20 

81.74 
81.83 

«i 

1.48 

11.79 
11.81 

4.80 
4-79 

81.94 
81.92 

26  j1-?0 
1  1-70 

10.03 
10.07 

4-77 
4.76 

83.50 
83.47 

44  | 

1-74 
1-73 

11.91 

11.88 

4-55 
4-54 

81.80 
81.85 

27j  1-43 
7  <  1-46 

10.38 
10.44 

5-22 
5-25 

82.97 
82.85 

45  j 

1-55 
i-54 

10.53 
10.46 

5.50 
5-52 

82.42 
82.48 

as}1''" 

1  1-54 

10.95 
1  1.  06 

4.86 
4-92 

82.64 
82.48 

46  1 

i  .60 
i  .60 

ii  .06 

11.13 

4.38 
4-39 

82.96 
82.88 

,«J  J-62 

29  ]  i.  62 

10.82 
10.95 

4.86 
4.89 

82.70 
82.54 

«l 

i  .60 

1.58 

11.85 
11.82 

4-93 
4.98 

81.62 
81.62 

3°  "|    l!&2 

11.45 
11.54 

4.56 

4-59 

82.36 
82.25 

48  j 

1.35 
1.40 

IO.2I 
IO.26 

5-47 
5-54 

82.94 
82.80 

31  ]  I>45 

11.49 
11.48 

4.26 

4-25 

82.80 
82.79 

49J 

1.42 
1.42 

8.36 

8-43 

4.87 
4-94 

85.35 
85.21 

32-j;:g 

11.78 
11.77 

4-84 
4.82 

82.00 
82.01 

50-j 

1.65 
1.65 

12.28 
12.28 

4.76 
4-75 

81.31 

81.32 

It  must  be  admitted  that  these  results  are  far  from  being  uniform. 
Indeed,  they  are  quite  the  opposite,  and  seem  to  bring  out  and  clearly 
to  establish  the  fact  that  there  are  extreme  variations  in  the  chemical 
composition  of  corn  grown  from  the  purest  seed  of  a  single  variety  and 
under  markedly  uniform  field  conditions.  Then  the  results  given  in  the 
experiment  preceding  this  are  to  be  considered  merely  as  averages  from 
a  large  number  of  small  samples  of  widely  varying  composition. 


152  BULLETIN    NO.     53.  \_Jlity> 

Following  are  the  maxima  and  minima  of  all  constituents  as  shown 
by  the  50  duplicate  analyses  : 

Ash.  Protein.  Fat.  Carbohydrates. 

Maximum 1.74  13.88  6.02  85.79 

Minimum 1.09  8.35  3-95  78.92 

Difference     ..0.65  5-53  2.07  6.87 

With  every  constituent  the  variation  is  greater  than  Flechig  found; 
with  13  different  varieties,  and  it  is  nearly  as  great  as  found  by  the  Con- 
necticut Experiment  Station  with  about  75  different  varieties  of  corn 
grown  under  90  presumably  different  conditions. 

This  comparison  is  facilitated  by  the  following  table  which  gives 
the  number  ot  samples  containing  the  different  constituents  in  amounts 
above  and  below  certain  specified  percentages;  columns  I.  and  II.  give 
the  numbers  of  such  samples1  from  my  results  and  those  of  the  Con- 
necticut Station,  respectively: 

Percent.             I  II  Percent.                I.   II. 

Ash                    above     1.70   i  5         below     i.io i     9 

Protein                 "        13.75   x  3             "         9.00 2     4 

Fat                        "         6.00 i  i             "         4.00 i     2 

Carbohyrates      "       85.00 5  3             "       79.00 i     4 

It  is  observed  that  the  number  of  samples  with  percentages  of  ash 
outside  of  these  extremes  is  2  with  my  results  and  14  with  the  Connecti- 
cut experiments.  This  is  in  accord  with  the  well  known  fact  that  the 
amount  of  ash  constituents  taken  up  by  plants  varies  largely  with  the 
amount  of  soluble  mineral  matter  in  the  soil,  somewhat  regardless  of 
the  needs  of  the  plant;  and  it  indicates  wide  variations  in  Connecticut 
soils  in  this  regard,  as  we  should  expect  to  be  the  case.  By  reference 
to  page  138  it  is  seen  that  the  percentages  of  ash  in  the  90  samples  varied 
from  0.91  to  2. 10. 

If  we  omit  the  ash,  the  number  of  percentages  of  all  constituents 
which  fall  outside  the  limits  given  above  is  n  with  my  results  from  50 
samples  and  16  with  the  Connecticut  results  from  90  samples. 

ANALYSES  OF  PARTS  OF  THE  EAR. — In  studying  this  question  30  dupli- 
cate analyses  were  first  made  on  different  parts  of  ears.  Five  ears  were 
divided  lengthwise  into  3  samples  each  in  the  following  manner:  If  the 
ear  were  i2-rowed,  3  samples  of  4  consecutive  rows  each  were  made; 
if  i6-rowed,  3  samples  of  5  consecutive  rows  each  were  made,  one 
row  being  left,  etc.,  etc. 

Duplicate  analyses  of  15  samples  thus  prepared  from  5  different 
ears  gave  the  following  results.  The  different  ears  are  distinguished  by 
the  letters  (a),  (b),  (c),  (d),  and  (e): 

1Not  single  determinations. 


1898.] 


CHEMISTRY  OF  THE  CORN  KERNEL. 


'53 


8(c)j 


Ash. 

Protein. 

Fat. 

Carbohy- 
drates. 

Ash. 

Protein. 

Fat. 

Carbohy- 
drates. 

1.42 
i-43 

10.79 
10.75 

4-57 
4.58 

83.22 
83.24 

'w\i$ 

10.  15 
10.20 

5.20 
5-i7 

83.29 
83.26 

1.48 
1-47 

10.97 
10.94 

4-54 
4-51 

83.01 
83.08 

io(d)|;;39 

10.46 
10.46 

4.28 
4.29 

83.87 
83.87 

1.50 
1.51 

10.66 
10.72  • 

4-53 
4-55 

83-31 
83.22 

n(d)-j'-43 

1  i  .42 

10.25 
10.27 

4.22 
4.20 

84.  10 
84.11 

i.5i 
i-52 

12.  OO 

11.98 

4.60 
4-59 

81.89 
81.91 

i2(d)^-43 
I  I-45 

10.09 
10.06 

4.16 

4-15 

84.32 
84-34 

1.49 
1.48 

12.  OI 
I2.O5 

4-57 
4-57 

8i.93 
81  .90 

„  {e*  J  1-34 
M-36 

11.19 

II  .20 

4.80 

4.78 

82.67 
82.66 

1.48 
1-47 

12.  ig 
12.  08 

4.85 
4.80 

81.48 
81.65 

/  \  i  I-3° 
14  (e)  {  1.28 

10.66 
10.62 

4.91 
4-89 

83-13 
83.21 

i-37 

1-37 

lO.Og 
IO.IO 

5-24 

83.30 
83-36 

,(e}\  1.36 

(e)}  1.36 

10.81 
10.92 

4-83 
4-79 

83.00 
82.93 

i  .31 

1-34 

10.14 

10.18 

5.08 

83.47 
83-30 

These  results  indicate  uniformity  in  the  composition  of  the  different 
parts  of  the  ear.  The  following  shows  the  greatest  total  variation  in 
the  6  single  determinations  of  each  constituent  in  any  one  ear;  and 
also  the  total  variation  between  the  different  ears: 

Ash.  Protein.  Fat.         Carbohydrates. 

In  any  single  ear 09  .58  .28  .55 

In  five  ears  24  2.13  1.09  2.86 

Another  lot  of  five  ears  was  selected  and  each  of  these  was  divided 
crosswise  into  3  samples  of  approximately  equal  amounts,  which  for 
convenience  are  designated  "tip,"  "middle,"  and  "butt,"  the  ears  being 
lettered  (f),  (g),  (h),  (i),  and  (j). 

The  duplicate  analyses  follow: 


/ 

ish. 

Carbohy-                                                                  Carbohy 
Protein.     Fat.      drates.                         Ash.     Protein.     Fat.      drates. 

16  (f)      I 
Tip         '/ 

.58 
•59 

11.78       5.09       81.55             24  (h)      j     .51       10.49       4.01       83.99 
11.76       5.10       81.55             Butt        |     .49       10.46       4.00       84.05 

17  (f)      I 
Middle   ( 

•58 
•  57 

12.22       5.13       81.07             25  (i)  •  j     .47       10.58       4.58       83.37 
12.26       5.03       81.14             Tip          /     .48       10.61       4.60       83.31 

18  (f)      j 
Butt        ) 

•  56 

.58 

12.36       5.04       81.04             26  (i)      \     .45       11.05       4-56       82.96 
12.42       5.03       80.97             Middle    /     .44       11.03       4.60       82.93 

19  (g)      \  > 
Tip         1  i 

•49 
•49 

11.99       4.86       81.66             27  (i)      \  1.47       11.03       4-48       83.02 
11.97       4-84       81.70             Butt        M.48       10.96       4.46       83.10 

20  (g)         \ 

Middle    ( 

1.51 
[.51 

12.49       4.77       81.23             28  (j)      j     .77       10.87       4-36       83.00 
12  49       4.76       81.24             Tip          j     .74       10.78       4.37       83.11 

21    (g)         I 

Butt        j 

[-5° 
i-5i 

13.02       4.57       80.91              29  (j)      \     .65       11.35       4-56       82.44 
13.10       4.59       80.80             Middle    (     .62       11.31       4.58       82  49 

22  (h)        j] 

Tip         j  i 

•37 
•35 

9.72       3.90       85.01             30  (j)      \     .71       11.32       4-28       82.69 
9-67       3.93       85.05             Butt        (     .72       11.28       4.29       82.71 

23  (h)      ( 
Middle  1 

i-37 
1-35 

10.07       3-98       84.58 
10.08       3-97       84.60 

154  BULLETIN    NO.     53. 

These  results  are  similar  to  those  in  the  preceding  experiment. 
The  following  shows  the  total  variation: 

Ash.  Protein.  Fat.        Carbohydrates. 

In  any  single  ear  ...........  16  1.13  .30  1.06 

In  five  ears  ................  42  3-43  i  .23  4.25 

It  is  observed  that  in  every  case  the  tip  is  lowest  in  protein  and  that 
usually  the  middle  is  lower  than  the  butt,  the  average  total  difference  in 
the  ear  being  0.73  per  cent,  and  the  widest  1.13  per  cent,  as  shown 
above1.  The  variation  in  ash  and  fat  is  small  and  shows  no  such  pecu- 
liarity. The  carbohydrates,  being  estimated  by  difference,  appear,  of 
course,  as  the  complement  to  the  sum  of  the  other  substances  and  show 
in  the  opposite  direction  approximately  the  variation  of  the  most 
variable  determinable  constituent. 

PARTIAL  ANALYSES  OF  SINGLE  KERNELS.  —  From  1009  separate  deter- 
minations Richardson'4  has  found  the  average  weight  of  100  kernels  of 
air-dry  corn  to  be  36.7  gms.  Allowing  10  per  cent,  for  moisture,  gives 
0.330  gms.  as  the  average  weight  of  the  dry  kernel.  This  weight  is  too 
small  for  a  very  exact  single  determination  of  a  single  constituent,  and, 
of  course,  no  attempt  has  been  made  to  do  more  than  that. 

The  ash  determination  was  made  by  incinerating  the  whole  kernel 
without  grinding,  the  weight  of  the  dry  matter  having  been  previously 
taken  after  drying  the  kernel  for  8  hours  in  a  current  of  hydrogen  at 
105°;  and  the  nitrogen  determination  was  made  on  the  whole  kernel 
after  drying  and  without  grinding,  the  digestion  proceeding  as  satisfac- 
torily as  with  ground  corn.  No  satisfactory  method  was  found  for  the 
determination  of  the  fat  in  a  single  kernel. 

The  ash  determinations  in  10  single  kernels  taken  from  as  many 
different  places  on  an  ear  gave  the  following  results  : 


Kernel, 

Ash, 

Ash, 

Kernel, 

Ash, 

Ash, 

weight. 

weight. 

per  cent. 

weight. 

weight. 

per  cent. 

I.  . 

...0.3579 

o  .  0048 

1-34 

6. 

0.3953 

0.0053 

1-34 

2.  . 

...0.2947 

0.0042 

1-43 

7- 

0.4507 

o  .  0066 

i  .46 

3-- 

...0.3985 

0.0052 

1.30 

8. 

0.4589 

o  .  0064 

1-39 

4-- 

...0.3585 

o  .  0046 

1.28 

9- 

.  .  .  .0.4211 

0.0062 

i-47 

5-. 

••  -0.3936 

o  .  0054 

1-37 

10. 

.  .  .  .0.5072 

o  .  0070 

I-3S 

For  further  work  on  the  ash  content  several  ears  of  corn  were 
selected,  and  from  each  a  sample  of  corn,  consisting  of  a  number  of 
rows  and  believed  to  fairly  represent  the  ear,  was  taken  and  its  percent- 
age of  ash  in  the  dry  matter  determined.  Then  for  the  special  investiga- 
tion of  the  ash  content  of  single  kernels  four  ears  from  the  lot  were 
chosen,  of  which  two  were  high  and  two  were  low,  comparatively,  in  the 

'It  will  be  seen  that  later  work  on  single  kernels  tends  to  confirm  and  establish 
this  as  a  characteristic  of  the  ear  of  corn. 

2U.  S.  Dept.  of  Agr.,  Div.  of  Chem    Bui.  (1884)  4,  82. 


i898.] 


CHEMISTRY    OF    THE    CORN    KERNEL. 


'55 


percentage  of  ash  as  previously  determined.  From  each  ear  10  kernels 
were  selected  at  approximately  equal  distances  apart  throughout  the 
length  of  the  ear,  the  kernels  being  numbered  from  i  to  10  and  the 
order  running  from  tip  to  butt.  The  data  from  the  ash  determinations 
in  the  single  kernels  and  also  the  percentage  of  ash  in  the  large  sample 
from  the  same  ear  are  given  below  : 


Ear  No.  i. 

—  Ash  =  i  .73 

per  cent. 

Ear  No.  2.  —  Ash  =  1.65  per  cent. 

Kernel, 

Ash, 

Ash, 

Kernel, 

Ash, 

Ash, 

weight. 

weight. 

per  cent. 

weight. 

weight. 

per  cent. 

I 

•  •  •  -O.3334 

0.0050 

i  .50 

i 

0.2933 

0.0048 

i  .64 

2 

.  o,  3367 

o  .  oo  5  3 

i  .57 

2 

O    27Q7 

o  .  0046 

M.     .   v*f 
I          64 

3 

.  .  .  .0.3662 

j  j 
o  .  0059 

1.61 

3 

0.2945 

o  .  0048 

*•     •   V*f 
1.63 

4 

.  .  .  .0.3901 

0.006  i 

1.56 

o  2551 

0.0042 

5 

.  .  .  .0.3417 

O  .OO')7 

.  jv 

i  .67 

0.3207 

0.0051 

I     .jg 

6 

.  o  3614 

J  1 

o  .  006  i 

i  .60 

6 

O    3OOS 

I          63 

7. 

.  .  .  0.3798 

0.0065 

*  .  **y 
I.7I 

7 

0.3346 

o  .  0056 

*             •         ^    J 

1.68 

8 

.  .0.4030 

o  .  0066 

I  .64 

8 

O    3144 

0.0052 

i  65 

g 

.  .0.4446 

O.OO73 

"f 
I  .64 

q 

o.  3463 

0.0059 

•   j 

i  .70 

/  J 

o  .  007  i 

»  .  «.f 

1.74 

IO 

o.  1627 

0.00^8 

•  / 
i  ,60 

Ear  No.  3. 

—  Ash  =  i  .  10 

•   /  T 

percent. 

Ear  No.  4.  —  Ash  =  i.n  percent. 

Kernel, 

Ash, 

Ash, 

Kernel, 

Ash, 

Ash, 

weight. 

weight. 

per  cent. 

weight. 

weight. 

per  cent. 

i 

.  .0.  2630 

0.0029 

I  .  IO 

- 

o  3080 

0.0035 

I     14 

2 

.  .  .  .0.  2591 

0.0028 

i.  08 

2 

O    34QQ 

O    OO43 

x  *  •L'r 

3- 

....0.2655 

o  .  0029 

1.09 

3-. 

*_*   .   W*f  J 

0.0038 

I.I3 

4- 

0.2887 

0.0031 

I  .  IO 

4-- 

.  .  .0.3422 

o  .  0040 

•17 

5- 

0.3077 

0.0033 

1.07 

5-- 

...0.3970 

O.OO45 

•13 

6. 

.  .  .  .0.3216 

0.0035 

1.09 

6.. 

...0.3514 

0.0043 

.22 

7- 

0.3363 

o  .  0036 

1.07 

?•• 

...0.3767 

o  .  0047 

•25 

8. 

0.3476 

0.0038 

I  .10 

8.. 

.  .  .0.4186 

0.0050 

.19 

9- 

0.3467 

0.0042 

I  .21 

9-. 

...0.4331 

o  .  0048 

.11 

10. 

.  .  .  .0.4042 

0.0045 

I  .  II 

IO.  . 

.  .  .0.4638 

0.0051 

.IO 

These  results  confirm  those  of  the  previous  experiments  in  indicat- 
ing uniformity  in  the  composition  of  the  ear  in  all  parts,  although  slight 
variations  are  found,  of  course.  It  may  be  noted,  however,  that  the 
variation  from  the  average  percentage  is  rarely  equivalent  to  more  than 
three-tenths  of  a  milligramme  in  the  weight  of  the  ash. 

In  the  work  on  the  protein  content  of  single  kernels,  5  ears,  3  of 
which  were  high  and  two  relatively  low,  in  protein  were  selected  from  a 
number  of  ears  in  a  manner  analogous  to  that  described  in  the  previous 
experiment. 

As  duplicate  determinations  were  not  made  with  single  kernels  the 
complete  analytical  data  of  this  work  are  reported. 

The  water  used  in  making  up  reagents  and  standard  hydrochloric 
acid  and  in  the  analytical  process  where  needed  had  been  twice  distilled, 
once  with  sulfuric  acid,  to  free  it  from  ammonia,  and  once  with  calcium 


156  BULLETIN    NO.     53. 

hydroxid  to  remove  carbon  dioxid  and  volatile  acids.  In  standardizing 
the  hydrochloric  acid  and  ammonia  solutions  the  same  automatic 
pipette  and  burette  were  employed  as  in  the  subsequent  analyses1.  The 
hydrochloric  acid  was  standardized  by  means  of  silver  nitrate,  a  method 
whose  details  I  have  previously  investigated2  and  found  to  be  exceed- 
ingly accurate.  Lacmoid  indicator  was  used  in  standardizing  the  am- 
monia, and  chemically  pure  cane  sugar  was  employed  in  making 
"blank"  determinations  to  find  the  "correction"  for  reagents.  Follow- 
ing are  these  data  : 

Standardizing  hydrochloric  acid. 
35  cc.3  HC1  gave  1.4103  and  1.4104  gms.  AgCl. 

Standardizing  ammonia. 
17.5  cc.  HC1  required  27.55  and  27.55  cc.  NH3. 

Blank  determinations  with  sugar. 

17.5  cc.  of  standard  hydrochloric  acid  were  taken  and  to  neutralize  the  excess 
of  acid  required 

27.47,  27.45,  and  27. 47  cc.  of  standard  ammonia  solution. 

The  atomic  weights4  used  are  :  Cl  =  35.453;  Ag  =  107.938;  N  =  14.041.  The 
factor,  6.25,  was  used  to  obtain  the  protein  equivalent. 

These  data  give  194933  as  the  logarithm  (mantissa)  for  the  weight 
of  protein  equivalent  to  one  cubic  centimeter  of  standard  ammonia. 

In  the  following  work  17.5  cc.  of  standard  hydrochloric  acid  were 
taken  in  each  determination,  and  the  volume  of  standard  ammonia  re- 
quired to  neutralize  the  excess  of  acid  is  given  in  the  tables  in  cubic 
centimeters  : 

Ear  No.  i. — Protein  =  13.06  per  cent.  Ear  No.  2. — Protein  =  13.87  percent. 

Kernel,  Ammonia  to  Protein,  Kernel,  Ammonia  to    Protein, 

weight.  neutralize.  per  cent.  weight,  neutralize,      per  cent. 

1  ....0.2945  25.12             12.46  i  ....0.3206  24.97  12.17 

2  ....0.3127  24.96             !2.54  2  ....0.3207  24.81           12.94 

3 0.2893  25.16             12.44                  3 0.3094  24.99           12.51 

4 0.2991  25.07             12.50  4     ...0.2841  24.97  I3-42 

5  ....0.3147  24.99             12.30                   5 0.3475  24-55  13-12 

6 0.3162  24.94              12.49                   6 0.2899  24.76  14-59 

7 0.3544  24-63              12.50                   7 0.2835  25.07  13.21 

8 0.3302  24.90             12.14                   8 0.3475  24.48  13-43 

9 0.3601  24.67              12.14                   9 0.3179  24.79  13-16 

10 0.3368  24.73  12.71  10 0.3301  24.50  14-05 


xlf  this  precaution  is  observed,  if  the  full  measure  of  acid  is  always  taken,  and 
if  the  graduation  of  the  automatic  ammonia  burette  is  strictly  uniform,  there  is  no 
special  necessity  for  the  apparatus  to  read  absolute  values. 

2Methods  of  Standardizing  Reagents. — Master  of  Science  Thesis,  Cornell  Uni- 
versity, 1894. 

3Twice  the  volume  of  the  automatic  pipette. 

^Ostwald,  Grundriss  der  allgemeinen  Chemie  (1890)  31. 


i898.] 


CHEMISTRY    OF    THE    CORN    KERNEL. 


157 


Ear  No.  3. 

Kernel, 

weight. 

I 

o  3626 

2 

0.3039 

3 

o.  3353 

4 

o.  3048 

5-- 

..0.3225 

6 

o.  3013 

7   • 

.  .  .0.2635 

8 

0.3204 

9 

0.3254 

10 

O.  3IQ1; 

Kernel, 

weight. 

i.  . 

.  .  .0.2819 

2.  . 

.  ..0.2682 

3-. 

.  .  .0.2378 

4.. 

.  .  .0.2641 

5-- 

.  .  .0.2891 

—Protein  =  12, 

,96  percent.     Ear  No.  4.—  Protein  =  7.59  per  cent. 

Ammonia  to 
neutralize. 

Protein, 
per  cent. 

Kernel.     Ammonia  to 
weight.      neutralize. 

Protein 
per  cent. 

24.79 

"•53 

i 

....0.2503 

26.27 

7-45 

25.07 

12.32 

2. 

..    .0.2432 

26.29 

7-54 

24-85 

12.19 

3- 

...  .0  2383 

26.29 

7.69 

25.02 

12.54 

4. 

.  .  .  .0.2118 

26.45 

7-47 

24.96 

12.  14 

5- 

.  .O    2752 

26.10 

7-74 

24-97 

12-95 

6 

.  .  O    27IQ 

25.95 

8.70 

25-30 

12.84 

7 

.  .  .  .0.2758 

25-97 

8.46 

Lost  by  accident.                  g 

.  .O    27O3 

8  60 

24.96 

I2.O4 

9 

.  .  .  ,o  2809 

8 

8  86 

24.86 

12.75 

10 

8 

8.  10 

Ear 

No.  5—  Protein 

8.40  per  cent 

Ammonia  to 

Protein 

Kernel,     Ammonia  to 

Protein 

neutralize. 

per  cent. 

weight. 

neutralize 

per  cent. 

26.07 

7.72 

6 

...  .0.  3002 

2"?    78 

8.76 

26.02 

8.41 

7 

.     O.273O 

•*  j  »  /*• 

25    QI 

8.89 

26.  19 

8.37 

8 

.  .  .  .0.2830 

*•  j  •  y  * 
2"5.83 

902 

26.06 

8.31 

9 

.  .  .  .0.2973 

j  -    j 
25.76 

.  w* 
8.96 

25-98 

8.02 

.  .  .  .0.2821 

25.86 

•^   •  -yv 

8.89 

The  concordant  evidence  of  30  duplicate  analyses  of  parts  of 
«ars,  of  50  ash  determinations,  and  of  50  protein  determinations  in 
single  kernels  would  seem  to  warrant  the  conclusion  and  to  establish 
the  fact  that  the  composition  of  the  ear  is  approximately  uniform 
throughout. 

Extended  investigations,  based  upon  the  facts  brought  out  in  these 
studies  of  the  proximate  composition  of  corn,  are  being  continued  by 
the  writer. 


PART  II.— THE  COMPLETE  COMPOSITION  OF  CORN. 
HISTORICAL. 

THE  ASH  OF  THE  CORN  KERNEL. — The  earliest  analysis  on  record  of 
the  ash  of  corn  is  evidently  that  made  by  De  Saussure1  reported  in  1804. 
Following  are  his  results: 

Potash 14 .  oo 

Phosphate  of  potash 47 . 50 

Chlorid  of  potash 0.25 

Sulf ate  of  potash 0.25 

Earthy  phosphates 36 .  oo 

Silica > i .  oo 

Metallic  oxids o.  12 

Loss..  0.88 


Researches  Chimiques  sur  la  Vegetation,  by  Theod.  De  Saussure  (1804)  351; 
Trans.  N.  Y.  State  Agr.  Soc.  (1848)  8,  727. 


158                                                               BULLETIN    NO.     53.  \_July, 

Subsequently  Letellier1  reported  the  following  analysis: 

Magnesia 17.00 

Lime 1.30 

Phosphoric  acid 50 . 10 

Silica 0.80 

Sulf uric  acid Trace 

Potash,  soda,  and  loss 30.80 

As  the  later  investigations  will  show,  the  analysis  of  Letellier  gives 

very  approximately  the  true  composition  of  corn  ash.  Much  less 
approximate  are  the  analyses  of  Salisbury,  of  which  he  reported2  several 
similar  to  the  following: 

Silica 1.45  2 . 65 

SO3 0.21  0.13 

P2°5 ? 50.96  49-31 

Iron  phosphate 4-35  o .  75 

Lime.... °-i5  °-45 

Magnesia .-,  . .    16.52  15. 49 

Potash 8.29  5.19 

Soda 10.91  19.18 

NaCl 0.25  0.90 

Cl o.  10 

Organic  acids 3.10  3.45 

Coal 1.75 

Later  analyses  by  Liebig  and  Kopp3,  Stepf4,  Way  and  Ogston''',  and 
Bibra6  gave  the  following  results: 

Liebig  Way  and 

and  Kopp.         Stepf.          Ogston.          Bibra.  Bibra. 

K20 30.74             28.80            28.37             24.33  26.75 

Na2O 3.50               1.74               1.50  3.85 

MgO 14.72             J4-90             13.60             16.00  J5-24 

CaO 3.06              6.32               0.57               3.16  2.56 

Fe2O3 0.84               i.si7             0.47               i.888  2.00" 

P2°s 44-50             44.97             53.69            49.36  47.47 

SO3 4.13             Trace.             i.oo  1.20 

SiO2 1.78             1.55               2.77  1.93 

Cl 0.50  ....  

In  1880  Wolff9  gave  the  following  as  the  average  of   15  analyses  of 
the  ash  of  corn: 


1  Annalen  der  Chemie  und  Pharmacie  (1844)  50,  403. 
2Trans.  N.  Y.  State  Agr.  Soc.  (1848)  8,  678. 
3Jahresbericht  iiber  die  Fortschritte  der  Chemie  (1856)  815. 
4 Journal  fiir  praktische  Chemie  (1859)  76,  88. 

5Liebig's  die  Chemie  in  ihre  Anwendung  auf  Agricultur  (1865)  1,  384. 
"Same  reference. 
7And  SO3  and  loss. 
"And  loss. 

"Wolff's  Aschen  Analysen  (1880);    Thorp's    Dictionary  of    Applied   Chemistry 
(1890)  1,  497. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  159 

K2O.       Na.jO.     MgO.       CaO.     Fe2O3.     P2O5      SO3         SiO2        Cl. 

29.8  I.I  15.5  2.2  0.8  45-6  O.8  2.1  O.Q 

Quite  recently  Scovell  and  Peter  have  reported1  a  somewhat  extended 
investigation  of  the  ash  of  corn  with  reference  to  its  content  of  fertil- 
izing elements.  Following  are  the  percentages  of  potassium  oxid  and 
phosphoric  oxid  in  the  pure  ash  as  found  in  8  samples: 

K20.  PZ0B.  K20.  P,05. 

28.38  48.52^  29.66  52.14 

28.98  51.85  29.95  53-03 

29.41  52.45  29.27  53.10 

29.38  52.75  28.18  51.42 

It  seems  evident  that  as  a  rule  the  ash  of  corn  contains  at  least  95 
per  cent,  of  the  phosphates  of  potassium  and  magnesium,  about  twice 
as  much  potash  as  magnesia  being  present. 

THE  PROTEIDS  OF  THE  CORN  KERNEL. — Zein,  the  most  important 
proteid  in  corn  was  discovered  and  named  by  Gorham  in  1821  (see 
page  130),  although  he  concluded  from  his  investigations  that  it  was  not 
a  nitrogenous  body.  The  zein  was  obtained  by  extracting  with  alcohol 
the  residue  of  powdered  corn  insoluble  in  water,  3.30  per  cent,  of 
zein  being  found.  By  subsequent  extraction  of  the  corn  with  dilute 
acid  and  alkali  2.75  per  cent,  of  what  was  thought  to  be  albumen  were 
obtained. 

Soon  after  the  publication  of  Gorham's  work  Bizio2  reported  an  in- 
vestigation of  corn  in  which  he  claimed  to  have  discovered  the  alcohol 
soluble  proteid,  and,  curiously  enough,  he  states  that  he  had  named  it 
zein,  from  the  Greek  word  meaning  "nourishing  substance"  because 
of  the  fact  that  it  was  a  nitrogenous  body.  He  points  out  several 
differences  between  his  zein  and  that  which  Gorham  had  found,  and 
mentions  especially  that  in  1820  Configliachi:i  had  obtained  ammonia 
from  zein  by  dry  distillation.  By  means  of  ether  Bizio  extracted  oil 
from  zein  and  then  found  that  the  residue  was  but  partially  soluble 
in  alcohol.  These  two  portions,  the  one  soluble  and  the  other 
insoluble  in  alcohol,  he  thought  to  be  two  different  substances  and 
to  be  identical  with  the  gliadin  and  zymom  which  Taddei4  had  found 
in  the  gluten  of  wheat.  He  gives  the  alcoholic  extract  the  following 
composition: 

Oil,  soluble  in  ether 20.0  per  cent. 

Gliadin,  soluble  in  alcohol 43-4 

Zymom,  insoluble  in  alcohol 36.6          " 


Kentucky  Agr.  Exp.  Station  Report  (1891)  16. 
-Journal  fur  Chemie  und  Physik  (1823)  37,  377. 
3Ibid.  (1823)  37,  383. 
JIbid.  (1820)  29,  514. 


l6o  BULLETIN    NO.     53.  \_Jutyi 

Salisbury1  obtained  "albumen"  from  corn  by  extracting  with 
water  and  coagulating  by  heat,  and  "  casein  "  from  the  filtrate  by 
precipitating  with  acetic  acid.  He  extracted  zein  and  oil  by  means  of 
alcohol  and  separated  them  by  evaporating  the  alcohol  and  extracting 
the  oil  with  ether. 

Evidently  because  Berzelius2  in  commenting  on  Gorham's  results, 
had  expressed  the  opinion  that  the  zein  of  corn  and  the  gluten  of  wheat 
were  identical,  Stepf3  assumed  and  stated  incorrectly  that  Gorham 
claimed  to  have  obtained  zein  by  kneading  corn  meal  with  water,  in  the 
same  manner  as  gluten  may  be  obtained  from  wheat;  and  he  tried 
repeatedly  but  in  vain  to  accomplish  such  result.  By  extracting  corn 
with  alcohol  and  purifying  the  extract  by  treating  it  with  water  and  with 
ether  to  remove  sugar  and  oil,  he  states  that  he  obtained  pure  zein  very 
similar  to  that  obtained  by  Gorham.  It  was  easily  soluble  in  alcohol, 
but  by  repeated  solution  and  evaporation  of  the  alcohol  the  zein  was 
partially  changed  into  a  modification  insoluble  in  alcohol.  Stepf  called 
the  two  modifications  plant  glue  (  Pflanzenleim}  and  plant  casein,  sub- 
stances already  known. 

Albumen  was  also  obtained  from  an  aqueous  extract  of  corn  by 
coagulating  with  heat.  The  dry  matter  of  corn  was  found  to  contain 
0.7  per  cent,  of  albumen  and  7.5  per  cent,  of  zein.  Stepf  further  states 
that  from  four  closely  agreeing  determinations  he  found  pure  zein  to 
contain  15.6  per  cent,  of  nitrogen. 

In  1869  Ritthausen  reported4  an  investigation  of  the  proteids  of  the 
corn  kernel.  Misled  by  Stepf's  erroneous  assumption,  Ritthausen 
vainly  endeavored  to  obtain  a  cohering  glutenous  mass  by  kneading 
corn  meal  with  water. 

Zein  was  obtained  to  the  amount  of  5  per  cent,  by  extracting 
powdered  corn  with  alcohol  and  (A)  by  evaporating  the  alcohol  and 
extracting  the  residue  with  ether,  or  (B)  by  precipitating  the  zein  in  the 
alcoholic  extract  by  the  addition  of  much  ether.  Zein  was  further  puri- 
fied (C)  by  repeated  treatment  with  alcohol  and  ether,  and  (D)  by  dis- 
solving in  o.  i  to  o.  15  per  cent,  potassium  hydroxid  solution,  precipitating 
with  dilute  acetic  acid,  redissolving  completely5  in  alcohol,  and 
precipitating  with  much  water. 


iTrans.  N.  Y.  State  Agr.  Soc.  (1848)  8,  727. 

2Jahresbericht  iiber  die  Fortschritte  der  physischen  Wissenschaften  (1823) 
2,  124. 

3Journal  fiir  praktische  Chemie  (1859)  76,  88. 

••Journal  fur  praktische  Chemie  (1869)  106,  471. 

5Ritthausen  points  out  that  this  action  shows  zein  to  not  consist  in  part  of  casein, 
which  would  have  formed  an  "  alkali  albuminate  "  insoluble  in  alcohol. 


i898.] 


CHEMISTRY  OF  THE  CORN  KERNEL. 


161 


Ultimate    organic    analyses    of    these    four  preparations  gave  the 
following  results: 


Carbon  . . . 
Hydrogen 
Nitrogen  . 

Sulfur 

Oxygen. . . 


A. 
54.66 

7-45 
15-50 

0.69 
21.70 


B. 

54-71 
7-50 
15-53 

22. l62 


C. 

54.76 

7-57 

15-45 

22.22 


D. 

54.66 
7-51 

15-85 
0.65 

21-33 


Average. 
54.69 

7-51 
15-58 

0.69' 

21-53 


The  fact  may  be  noted  that  these  results  were  not  corrected  for  the 
ash  content  of  the  zein,  which  it  is  stated  was  insignificant;  and  also  the 
more  important  fact  that  the  nitrogen  determinations  of  both  Stepf  and 
Ritthausen  were  made  by  the  method  of  Varrentrap  and  Will3  employing 
the  old  atomic  weights  of  platinum  (197.2)  and  nitrogen  (14).  I  have 
recalculated  their  results  using  the  revised  atomic  weights  (Pt— 194.8; 
N=i4.o4i)4  and  find  Stepf's  average  of  four  determinations  to  be  15.84 
per  cent,  nitrogen  and  the  average  of  Ritthausen's  results5  to  be  15.82 
per  cent,  nitrogen,  in  zein,  while  preparation  (D)  alone  gives  16. 10  per 
cent,  nitrogen. 

By  repeated  solution  in  alcohol  and  evaporation  of  the  solvent, 
Ritthausen  obtained  zein  which  was  insoluble  in  alcohol  "dilute  or 
strong,  warm  or  cold."  He  states  positively  that  zein  (or  Maisfibrin,  as 
he  prefers  to  call  it)  is  not  a  mixture  of  proteid  bodies  but  a  single 
homogeneous  substance. 

After  the  alcoholic  extraction  of  the  corn  was  complete,  the  residue 
was  extracted  with  0.25  per  cent,  potassium  hydroxid  solution,  and  the 
extracted  proteids  precipitated  by  acetic  acid.  About  0.5  per  cent,  of 
substance  was  thus  obtained  from  corn,  which  Ritthausen  has  since 
referred6  to  as  globulin.  He  gives  the  following  as  the  composition  of 
the  ash-free  substance: 

Carbon    51.41 

Hydrogen 7 . 19 

Nitrogen 17.72 

Oxygen  and  Sulfur 23 . 68 


1  Sulfur  determination  in  (D)  was  not  considered  trustworthy. 

2 Should  be  22.26  evidently. 

3Annalen  der  Chemie  und  Pharmacie  (1841)  39,  257. 

4Ostwald,  Grundriss  der  allgemeinen  Chemie  (1890)  31. 

°I  have  checked  this  recalculation  from  the  weight  of  zein  employed  and  of 
platinum  found  as  reported  in  Ritthausen's  analytical  data,  and  find  that  he  used 
atomic  weights  as  stated  above. 

6Landwirtschaftliche  Versuchs-Stationen  (1896)  47,  391. 


1 62  BULLETIN    NO.    53  \_Juty, 

In  1877  Weyl1  pointed  out  that  a  10  per  cent,  solution  of  sodium 
chlorid  extracted  from  the  powdered  corn  kernel  a  globulin  proteid 
which  coagulates  at  75°. 

The  corn  proteids  soluble  in  sodium  chlorid  solution  have  been 
very  thoroughly  investigated  by  Chittenden  and  Osborne2  and  the  pre- 
vious work  on  zein,  the  alcohol-soluble  proteid,  was  carefully  repeated. 

With  10  per  cent,  sodium  chlorid  solution  they  extracted  from 
powdered  corn  about  0.5  per  cent,  of  proteid  matter  from  which  they 
were  able  to  separate  at  least  four  different  bodies  now  known3  as  (i) 
proteose,  (2)  very  soluble  globulin,  (3;  maysin  (globulin),  and  (4)  edestin 
(globulin).  As  the  salt  is  removed  from  the  solution  by  dialysis,  the 
maysin  and  edestin  precipitate,  the  other  bodies  remaining  in  solution. 
By  long  continued  dialysis  a  part  of  the  very  soluble  globulin  is  pre- 
cipitated, the  remainder  (originally  thought  to  be  albumen  by  Chitten- 
den and  Osborne)  being  precipitated  by  hydrochloric  acid.  Of  the 
proteose,  a  part  (also  first  called  albumen)  was  obtained  by  coagulating 
with  heat,  and  the  remainder  was  precipitated  with  alcohol.  After  re- 
dissolving  in  salt  solution  the  mixture  of  the  two  precipitated  globulins, 
maysin  was  separated  from  edestin  by  coagulating  with  heat,  the 
edestin  being  finally  precipitated  as  the  salt  was  removed  by  dialysis. 
Other  methods  were  also  employed  to  separate  these  two  globulins, 
based  upon  the  fact  that  maysin  is  readily  soluble  in  extremely  dilute 
salt  solutions,  while  edestin  requires  greater  concentration  of  salt  for 
solution. 

The  averages  of  all  analyses  of  each  of  these  four  proteids  follow: 

Very  soluble 

Proteose.  globulin.  Maysin.  Edestin. 

Carbon 51.30  52.84  52.68  51.71 

Hydrogen  .    .   6.71  6.82  7.02  6.85 

Nitrogen 16.35  !5-38  16.78  18.12 

Sulfur ,.   2.00  1.37  1.30  o'86 

Oxygen 23.64  23.59  22.22  22.46 

The  different  preparations  of  proteose  and  of  the  very  soluble 
globulin  show  some  wide  differences  in  composition  which,  it  is  believed, 
are  "simply  due  to  their  alteration  by  the  process  made  use  of"  in  their 
separation.  It  was  found  "that  these  soluble  bodies  are  exceedingly 
prone  to  change."  By  the  long  continued  action  of  water  and  salt 
solutions  an  insoluble  modification  of  variable  composition  was  pro- 
duced from  maysin  and  the  very  soluble  globulin. 


^eitschrift  fur  physiologische  Chemie  (1877)  1,  84. 
2  American  Chemical  Journal  (1891)  13,  453,  529;  (1892)  14,  20. 
3Osborne,  Conn.  Agr.  Exp.  Station  Report  (1896)  20,  391.     To  avoid  confusion 
these  terms  are  here  used  instead  of  myosin,  vitellin,  etc. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  163 

Following  are  the  maxima  and  minima  of  the  several  constituents 
determined  in  all  analyses  of  proteose,  very  soluble  globulin,  and  the 
insoluble  modification  : 

Very  soluble  Insoluble 

Proteose.                      globulin.  modification. 

Carbon 52.061050.07         53.531052.36  53.95*051.97 

Hydrogen 6.91   "    6.54          6.90  "    6.74  7.05   "    6.90 

Nitrogen 17.28   "15.78         15.69   "15.16  16.82   "15.87 

Sulfur 2.37   "     1.62           1.48   "     1.26  1.16   "     1. 12 

The  several  analyses  of  both  maysin  and  edestin  agree  within  nar- 
row limits. 

After  the  extraction  with  salt-solution  was  completed,  zein,  the 
most  abundant  proteid  in  the  corn  kernel,  was  obtained  by  extracting 
with  75  per  cent,  alcohol  "at  about  50°,  and  highly  purified  by  repeated 
solution  in  alcohol  and  precipitation  with  water,  the  last  traces  of  oil 
being  removed  by  final  extraction  with  ether* 

By  warming  with  water  or  very  dilute  alcohol  zein  was  readily 
changed  into  the  insoluble  modification. 

Following  is  the  composition  of  zein  as  shown  by  the  averages  of 
several  closely  agreeing  analyses  of  both  the  soluble  and  the  insoluble 
modifications: 

Soluble  zein.  Insoluble  zein. 

Carbon 55-28  55 .15 

Hydrogen 7.27  7  •  24 

Nitrogen 16 . 09  16.22 

Sulfur 0.59  062 

Oxygen 20 . 77  20 . 77 

The  statement  is  made  that  "corn  meal,  after  thorough  extraction 
with  "salt  solution  and  warm  dilute  alcohol,  yields  little  proteid  matter 
to  dilute  solutions  of  potassium  hydroxid  (0.2  per  cent.)." 

Osborne's  more  recent  investigations1  have  shown  this  assumption 
to  be  very  erroneous;  and  he  now  estimates  such  treatment  to  yield 
3.15  percent,  of  proteid  soluble  in  0.2  per  cent,  potassium  hydroxid 
solution.  It  is  noteworthy  that  this  quantity  is  seven  times  the  total 
amount  of  the  several  proteids  extracted  by  salt-solution.  Analyses  of 
the  purified  preparation  gave  the  following  results  : 

Carbon 51.26 

Hydrogen 6.72 

Nitrogen 15 . 82 

Sulfur o .  90 

Oxygen 25 . 30 


JConn.  Agr.  Exp.  Station  Report  (1896)  20,  391. 


164  BULLETIN    NO.     53.  [/ufy, 

The  quantities  of  the  different  proteids  in  the  corn  kernel  are  esti- 
mated as  follows  : 

1.  Proteose,  soluble  in  pure  water 0.06  per  cent. 

2.  Very  soluble  globulin 0.04  "  " 

3.  Maysin,  soluble  in  extremely  dilute  salt-solutions 0.25  "  " 

4.  Edestin,  soluble  in  more  concentrated  salt-solutions. .  .o.  10  "  " 

5.  Zein,  soluble  in  alcohol 5 . oo  "  " 

6.  Proteid  matter,  soluble  in  dilute  alkalies 3 .15  "  " 

7.  Proteid  matter1  insoluble  in  any  of  these  solvents  . . .  .1  .03  "  " 

Osborne  has  calculated  the  mean  percentage  of  nitrogen  in  corn 
proteids  to  be  16.057. 

In  a  review  of  the  percentages  of  nitrogen  in  the  proteids  of  various 
vegetable  substances,  Ritthausen2  places  corn  in  the  class  with  proteids 
containing  16.67  Per  cent,  of  nitrogen,  and  uses  the  factor  6.00  for  cal- 
culating protein  from  the  percentage  of  total  nitrogen.  It  is  observed, 
however,  that  Ritthausen  has  misquoted  his  own  results  on  the  composi- 
tion of  zein,  as  will  be  seen  from  the  following  : 

Original3.  As  quoted. 

Carbon 54  .-69  54 . 69 

Hydrogen 7.51  7  •  5° 

Nitrogen 15.58  16.33 

Sulfur 0.69  0.69 

Oxygen   21.53  21.53 

An  error  of  0.05  appears  in  the  hydrogen  and  of  0.75  in  the  nitro- 
gen, and  furthermore  the  total  is  100.80,  clearly  showing  that  the 
analysis  is  misquoted.  His  analysis  of  globulin  is  quoted  correctly. 

In  this  connection  it  is  interesting  to  note  that,  if  we  take  Ritt- 
hausen's  determinations  of  zein  (containing  15.58  per  cent,  of  nitrogen) 
as  5.00  per  cent,  of  the  corn,  and  globulin  (containing  17.72  per  cent, 
of  nitrogen)  as  0.50  per  cent,  of  the  corn,  and  recalculate  the  nitrogen 
according  to  the  revised  atomic  weights  of  platinum  and  nitrogen, 
which  show  zein  to  contain  15.82  per  cent,  and  globulin  17.99  per  cent, 
of  nitrogen,  we  then  find  the  mean  percentage  of  nitrogen  in  the  pro- 
teids to  be  16.02,  which  is  practically  identical  with  Osborne's  result, 
and  proves  conclusively  that  with  our  present  knowledge  we  are  to  use 
6.25  as  the  factor  for  estimating  protein  from  the  total  nitrogen  content 
of  corn. 

THE  CARBOHYDRATES  OF  CORN. — Gorham  and  Bizio,  to  whose  work 
reference    has    already    been   made,    separated   sugar,    gum,    fiber,  and 


Nitrogen  in  residue  from  100  parts  of  corn  multiplied  by  the  factor  6.25. 
2Landwirtschaftliche  Versuchs-Stationen  (1896)  47,  391. 
3Journal  fiir  praktische  Chemie  (1869)  106,  483. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  165 

starch  in  the  carbohydrate  group,  with  the  following  results,  the  starch 
being  estimated  by  difference  : 

Carbohydrates.                                                          Gotham.  Bizio. 

Sugar 1.59  0.90 

Gum 1.92  2.29 

Fiber 3.30  7.71 

Starch 84.60  80.91 

In  connection  with  his  researches  upon  the  starch  content  of  many 
vegetable  substances  including  corn,  Krocker1  showed  the  absence  of 
appreciable  amounts  of  sugar  or  dextrine  in  the  ripe  seeds  of  cereals. 
Mitscherlich  is  quoted  as  having  reached  the  same  conclusion. 
Krocker's  method  for  determining  starch  was  by  hydrolysis  and  fer- 
mentation, the  amount  of  starch  being  calculated  from  the  weight  of 
carbon  dioxid  liberated.  In  modern  chemistry  the  relations  are  ex- 
pressed by  the  following  equations,  in  which  the  starch  first  takes  up 
water  and  is  converted  into  glucose-sugar  by  the  catalytic  action  of 
acids: 

C6H1005+H20=C6H1206 

and  then  the  sugar  is  decomposed  into  alcohol  and  carbon   dioxid  by 
yeast, 

C6H12O6=2C2H5OH-f2CO,. 

In  case  a  measurable  quantity  of  hexose-sugars  were  present  it  was 
determined  by  fermentation  previous  to  the  hydrolysis  of  the  starch. 

Duplicate  determinations  on  a  sample  of  corn  containing  14.96  per 
cent,  of  water  gave  the  following  results: 

Corn  taken 3.35  2.98    gms. 

Carbon  dioxid  found   1.02  0.92       " 

Starch  equivalent 1.877  1.693     " 

Starch  in  dry  matter 65.88  66.80    percent. 

Aside  from  the  determination  of  fiber  as  commonly  made  and  reported 
in  proximate  analyses  and  Atwater's  estimation  of  sugar  (see  page  134), 
nothing  further  of  importance  concerning  the  chemical  composition  of 
the  carbohydrates  of  corn  is  found  until  1887,  when  Archbold2  gives  the 
following  percentages  of  different  carbohydrates  in  corn,  as  representing 
"the  average  of  many  samples  analyzed  in  the  course  of  one  year's 
working  "  in  a  large  starch  factory: 

Water 1 1 . 20  Dry 

Starch  54 .80  61.71 

Cellulose .   16.40  18.47 

Gum  and  sugar 2.90  3.27 


« 
1  Annalen  der  Chemie  und  Pharmacie  (1846)  58,  212. 

-Journal  Society  Chemical  Industry  (1887)  6,  84 


1 66  BULLETIN    NO.     53. 

Archbold's  report  shows1  that  55.6  per  cent,  of  starch  are  actually 
obtained  from  corn  (dry  basis)  in  the  commercial  process  of  starch 
manufacture,  and  that  several  different  by-products  still  contain  traces 
of  starch. 

In  1889  Washburn2  reported  an  investigation  of  the  cane  sugar  con- 
tent of  corn.  By  extracting  1400  gms.  of  ordinary  field  corn,  to  which 
3  gms.  of  magnesia  had  been  added  to  prevent  possible  inversion  of 
sugar,  with  72  per  cent,  alcohol,  shaking  the  solution  with  ether  to 
separate  fat,  and  purifying  the  sucrose  in  the  filtered  aqueous  layer  by 
repeated  precipitation  as  strontium  sucrate  and  decomposition  of  the 
precipitate  by  carbon  dioxid  (method  of  Schultze3),  1.105  gms-  ot  pure 
cane  sugar  were  obtained  by  crystallization.  American  sweet  corn 
yielded  larger  amounts,  10.5  gms.  of  sugar  being  obtained  from  2000 
gms.  of  corn.  Washburn  states  that  all  of  the  sugar  in  the  co"rn  is  not 
obtained  by  this  process. 

Marcacci4  has  found  over  i  per  cent,  of  sugar  in  corn. 

Pentosans  (C5H8O4),  which  are  also  termed  wood  gum  and  hemi- 
cellulose,  were  found  in  corn  by  Stone5.  These  carbohydrate  bodies6 
yield  pentoses  (C5H10O5),  also  called  penta-glucoses,  by  hydrolysis  with 
dilute  acids  (C5HgO4+H2O  =  C5H10O6),  and  furfurol  (C^O,)  by  dis- 
tillation with  moderately  concentrated  acids  (C5HaoOr) — 3H2O  =  C5H4O2), 
reactions  which  serve  as  a  basis  for  their  quantitative  determination. 
Either  the  pentose  is  determined  by  Fehling's  method7  for  reducing 


'Based  upon  six  years'  experience  as  chemist  to  a  starch  factory. 

2Uber  den  Rohrzucker  des  Maiskorns,  etc  ,  —  Inaugural  Dissertation  zur 
Erlangung  der  Doctorwiirde, — Gottingen  (1889);  Journal  fiir  Landwirtschaft  (1889) 
37,  503. 

3Landwirtschaftliche  Versuchs-Stationen  (1887)  34,  403. 

4Le  Stazioni  Speriment,  Agrar.  Ital.  (1889)  17,  266;  Central-Blatt  fur  Agri- 
cultur-Chemie  (1890)  19,  352. 

5American  Chemical  Journal  (1891)  13,  73. 

6Two  pentosans  are  well  known:  Xylan,  found  quite  commonly  in  grains  and 
grasses;  and  araban,  occurring  especially  in  gums  such  as  arabic,  tragacanth,  cherry, 
etc.  Xylan  and  araban  have  the  same  empirical  molecular  formula,  but  they 
may  be  distinguished  by  the  difference  in  the  specific  rotation  and  melting  points  of 
the  respective  pentoses,  xylose  and  arabinose,  into  which  they  are  converted  by 
hydrolysis.  For  xylose  [a]D  =  i8°  to  19°  and  M.  P.  =  144°  to  145°;  while  for 
arabinose  [a]o=io3°  to  105°  and  M.  P.  =  i54°  to  157°.  Cf.  Koch,  Pharmaceutische 
Zeitschrift  fiir  Russland  (1886)  25,  619  and  other  pages;  Berichte  der  deutschen 
chemischen  Gesellschaft  (1887)  20,  III,  145;  Bauer.  Landwirtschaftliche  Versuchs- 
Stationen  (1889)  36,  304;  Stone  and  Tollens,  Annalen  der  Chemie  (1888)  249,  227; 
Wheeler  and  Tollens,  ibid.  (1889)  254,  304;  Schulze,  Zeitschrift  fur  physiologische 
Chemie  (1890)  14,  227;  (1892)  16,  387;  (1894)  19,  38. 

7Bauer,  Landwirtschaftliche  Versuchs-Stationen  (1889)  36,  304;  Stone,  Ameri- 
can Chemical  Journal  (1891)  13,  78. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  167 

sugars;  or  the  furfurol  is  determined,  preferably  by  precipitation  with 
phenyl  hydrazine  as  a  hydrazone  (CsH^ONgHCgHj)1. 

Stone  found  corn  bran  to  contain  1.25  to  2.67  per  cent,  of  pento- 
sans.2 Schulze,3  after  separating  considerable  other  matter  from  corn 
bran,  obtained  a  residue  which  yielded  43.37  per  cent,  of  a  pentosan 
which  he  showed  to  be  xylan.4 

In  1896  Stone5  reported  a  somewhat  extended  study  of  the  carbo- 
hydrates of  corn,  in  which  sucrose,  dextrine,  starch,  pentosans,  and 
fiber  were  determined  quantitatively.  The  general  method  employed 
may  be  briefly  described  as  follows: 

Sucrose. — Finely  ground  corn  meal  was  extracted  with  95  per  cent, 
alcohol  which  was  then  evaporated  nearly  to  dryness,  the  residue  taken  up 
with  water,  treated  with  hydrochloric  acid,  the  inverted  sugar  estimated 
by  Fehling's  solution  and  calculated  to  sucrose. 

Dextrine. — The  residue  of  meal  was  extracted  with  cold  water  which 
was  then  evaporated  to  a  small  volume,  the  dextrine  being  precipitated 
by  alcohol,  inverted  by  hydrochloric  acid,  and  estimated  by  Fehling's 
solution. 

Starch. — A  known  proportion  of  the  residue  of  meal  was  treated 
with  malt  extract,  the  solution  hydrolysed  and  the  sugar  obtained 
estimated  by  Fehling's  solution,  and  calculated  to  starch. 

Pentosans. — The  residue  from  the  starch  determination  was  boiled 
with  i  per  cent,  hydrochloric  acid,  the  pentose  formed  estimated  by 
Fehling's  solution  and  calculated  to  xylan. 

Fiber. — The  residue  still  remaining  was  boiled  with  1.25  per  cent, 
sodium  hydroxid,  and  the  insoluble  matter  (less  ash)  given  as  fiber. 

A  sample  of  corn  which  contained  80.69  Per  cent,  of  total  carbo- 
hydrates, when  estimated  "by  difference,"  gave  by  the  above  method 
the  following  results: 

Sucrose o .  27  per  cent. 

Dextrine 0.32 

Starch    42.50         " 

Pentosans 5. 14 

Fiber 1.99 

Total  carbohydrates 50.22         " 

'Flint  and  Tollens,  Landwirtschaftliche  Versuchs-Stationen  (1893)  42,  381.  Cf. 
Berichte  der  deutschen  chemischen  Gesellschaft  (1891)  24,  II,  3575;  (1892)  25,  II, 
2912. 

2The  results  were  published  (American  Chemical  Journal  (1891)  13,  73)  in  terms 
of  furfuramid,  but  are  here  calculated  to  pentosan. 

3Zeitschrift  fiir  physiologische  Chemie  (1894)  19,  41. 

1The  statement  by  Stone  (U.  S.  Dept.  of  Agr..  Exp.  Station  Bui.  (1896)  34,  16) 
that  Tollens  and  Flint  (Berichte  der  deutschen  chemischen  Gesellschaft  (1892)  25,  II, 
2916)  had  estimated  the  amount  of  pentosans  in  corn  bran  to  be  38  17  per  cent, 
appears  to  be  erroneous,  as  the  work  referred  to  was  with  corn  cobs  (Maiskolben) . 

r>U.  S.  Dept.  of  Agr.,  Exp.  Station  Bui.  (1896)  34. 


1 68  BULLETIN    NO.    53. 

In  discussing  his  results,  Dr.  Stone  says: 

"  This  method  not  only  permits  the  separation  of  the  more  delicate  and  easily 
decomposed  carbohydrates  from  those  which  offer  greater  resistance  to -reagents,  but 
from  the  very  beginning  of  the  process  any  carbohydrate  not  wholly  removed  at  any 
particular  step  would  hardly  fail  of  being  detected  at  the  next  succeeding  and  more 
searching  reaction.  It  is  considered  pertinent  to  the  subject  under  discussion  to  call 
attention  to  the  apparent  discrepancy  between  less  than  50  percent,  of  carbohydrates 
found  in  our  most  prominent  cereal  grains  by  direct  and  fairly  accurate  methods  of 
determination  and  the  70  to  80  per  cent,  commonly  ascribed  to  them  by  the  indirect 
method  of  estimating  '  by  difference.'  From  20  to  30  per  cent,  of  the  grain  or  flour 
is  not  accounted  for.  Under  the  conditions  this  matter  cannot  be  conceived  of  as 
possessing  a  similar  nature  to  the  sugars,  starches,  or  even  the  more  easily  soluble 
forms  of  gum  or  celluloses." 

When  we  remember  that  Krocker  had  shown  (see  page  165)  by  a  direct 
and  positive  method  that  corn  .contains  over  65  per  cent,  of  ferment- 
able1 carbohydrates  (at  least  almost  entirely  starch),  and  that  Archbold, 
from  long  experience  in  the  manufacture  of  corn-starch,  reports  over 
60  per  cent,  of  starch  present  in  corn  and  at  least  55  per  cent,  actually 
recovered  in  the  commercial  process  (see  page  166),  the  previously  exist- 
ing evidence  of  an  error  in  Stone's  results  is  apparent.  Dr.  Stone  has 
subsequently  discovered  and  reported8  a  large  error  in  the  starch  de- 
termination, due  to  the  use  of  too  dilute  hydrochloric  acid  and 
consequent  imperfect  hydrolysis.  The  percentage  of  starch  is  now 
given  as  65.45  instead  of  42.50  as  first  reported.  The  total  carbo- 
hydrates thus  found  by  determination  become  73.17  per  cent,  as 
compared  with  80.69  per  cent,  estimated  by  difference.  Dr.  Stone 
concludes  that: 

"This  discrepancy  may  arise  from  one  of  two  sources,  tviz. :  i.  Error  in  the 
determination  of  the  carbohydrates.  2.  The  existence  of  a  substance  which  is  free 
of  nitrogen  and  is  of  a  character  not  usually  ascribed  to  carbohydrates  and  resistant 
to  the  ordinary  reactions  for  such.  While  the  first  alternative  is  not  excluded,  the 
writer  is  inclined  to  the  latter  conclusion  and  expects  to  continue  the  investigation 
along  this  line." 

In  a  recent  report  of  extended  investigations  of  methods  for  the 
estimation  of  starch,  Wiley  and  Krug3  refer  to  their  experiments  with 
the  conversion  of  starch  into  maltose  and  dextrine  by  the  use  of  malt 
extract,  as  follows: 

"  The  residues  from  the  diastase  digestion  were  all  thoroughly  washed  with  hot 
water  and  then  examined  with  iodine  under  the  microscope.  In  every  case  a  large 
number  of  cells  was  found  which  contained  undigested  starch,  showing  that  the 
sample4  had  not  been  ground  to  a  sufficient  degree  of  fineness.  This  is,  therefore, 


JThe  pentosans  are  classed  as  strictly  non-fermentable  carbohydrates.  Cf. 
Koch,  Pharmaceutische  Zeitschrift  fur  Russland  (1886)  25;  Stone  and  Tollens, 
Annalen  der  Chemie  (1888)  249,  257;  Stone,  American  Chemical  Journal  (1891)  13,  82. 

2 Journal  American  Chemical  Society  (1897)  19,  183,  347. 

3Ibid.     (1898)  20,  255 

4  A  sample  of  wheat  previously  analyzed  by  Stone. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  169 

another  source  of  error  in  Professor  Stone's  work.     The  sample  was  then  reground 

and  the  starch  determined The  residues  were  again  examined  and  in  every 

case  found  free  from  starch,  showing  that  the  conversion  had  been  complete.     . 

.     The  number  for  starch  thus  obtained,  added  to  our  per  cents,  of  the  other  con- 
stituents gives  us  a  total  of  99.28." 

In  summarizing  their  results  Wiley  and  Krug  express  the  following 
opinion: 

"The  small  quantity  of  matter  unaccounted  for  in  the  cereal  grains  is  doubtless 
of  a  carbohydrate  nature,  belonging  to  that  complex  class,  pentosan-ligno-celluloses, 
whose  chemical  and  physical  properties  are  so  nearly  alike  as  to  make  their  exact 
separation  and  determination  extremely  difficult.  The  quantity  of  these  undeter- 
mined bodies  in  cereal  grains  is  very  minute." 

THE  OIL  OF  CORN. — The  presence  of  oil  in  the  corn  kernel  was  dis- 
covered by  Bizio1  in  1823.  A  partial  analysis  by  Hoppe-Seyler2  gave 
the  following  as  the  percentage  composition3  of  the  oil: 

Cholesterol 2 . 65 

Protogon 3-95 

Saponifiable  fats  etc 93-4° 

The  statement  is  made  that  the  oil  contains  stearin,  palmitin,  and 
much  olein,  and  the  melting  point  of  the  fatty  acids  is  given  as  51°  to 
54°  F.  [n°]  to  12°  C.]. 

Some  of  the  so  called  physical  and  chemical  "  constants,"  which 
have  been  determined  by  several  investigators  are  given  below: 

Specific  gravity  Unsaponifiable       lodin 

of  oil.  substance,  absorption, 

(at  i5°C.)  (percent.)  (per  cent.) 

Spuller4 1.35  "9-7 

Smith5 0.9244  ....  122.9 

Hart6 0.9239  1.55  117.0 

Rokitianski7... 0.8360                 75.8 

The  oil  used  by  Spiiller  was  the  ordinary  ether  extract.  Rokitianski 
used  a  petroleum  ether  extract.  Hart  worked  with  a  "dark  brown" 
sample  presumably  found  on  the  market.  Smith's  material  was  obtained 
on  the  market,  but  was  of  a  "  bright  golden  color"  and  was  probably 
a  fair  sample  of  corn  oil. 


'Journal  fiir  Chemie  und  Physik  (1823)  37,  377. 

2Medicinische-Chemische  Untersuchungen,  1,  162;  Bulletin  Society  Chimique 
de  Paris  (1866)  [2]  6,  342;  Jahresbericht  iiber  die  Fortschritte  der  Chemie  (1866)  698. 

3I  have  not  been  able  to  see  Hoppe-Seyler's  original  paper.  Presumably  the 
protogon  is  the  substance  now  termed  lecithin,  and  the  methods  employed  in  esti- 
mating it  and  cholesterol  were  similar  to  those  which  are  discussed  herein. 

-•Polytechnisches  Journal  (Dingier)  (1887)  264,  626. 

•"'Journal  Society  Chemical  Industry  (1892)  11,  504. 

elbid.  (1894)  13,  257,  from  Chem.  Zeit.  17,  1522. 

7lnaugural  Dissertation,  St.  Petersburg  (1894);  Pharmaceutische  Zeitschrift  fiir 
Russland  (1894)  33,  712;  Chemisches  Central-Blatt  (1895)  [4]  7,  I,  22. 


1 70  BULLETIN    NO.     53.  [faty, 

Spiiller  observed  that  the  oil  absorbed  no  oxygen  from  the  air 
even  after  fourteen  days'  exposure.  Smith  states  that  the  freezing  point 
of  the  oil  is  below  — 20°.  Hart  gives  the  melting  point  of  the  fatty 
acids  as  25°.  Rokitianski  reports  further  qualitative  chemical  work 
which  showed  the  oil  to  contain  oleic  and  linolic  acids.  It  is  evident 
from  the  specific  gravity  and  the  iodin  absorption  that  the  material  with 
which  he  worked  was  not  ordinary  corn  oil. 

Willey  and  Bigelow1  have  recently  found  the  heat  of  combustion  of 
oil  of  corn  to  be  9280  calories  per  gramme. 

EXPERIMENTAL. 

In  a  preliminary  study  a  small  amount  of  oil  was  obtained  by 
collecting  the  ether  extract  from  a  large  number  of  proximate  analyses 
of  corn.  In  this,  advantage  was  taken  of  the  fact  that  the  oil  is  moder- 
ately soluble  in  alcohol  when  hot  and  but  slightly  so  at  ordinary  temper- 
atures.2 

The  oil  was  transferred  from  the  small  flasks,  used  in  its  extraction, 
by  means  of  hot  alcohol  to  a  single  vessel.  On  cooling  the  oil  precipi- 
tated and  settled  to  the  bottom,  the  alcohol  being  each  time  decanted 
from  the  collected  oil  and  used  in  transferring  the  next  lot.  Finally 
the  alcohol  was  evaporated  and  the  oil  dried  to  constant  weight  in  a 
water  oven.  When  freshly  obtained  from  white  dent  corn  the  oil  is 
nearly  colorless,  but  on  standing  a  pale  yellow  and  finally  a  deep  golden 
color  develops,  plainly  indicating  a  gradual  change  in  its  condition, 
presumably  due  to  absorption  of  oxygen.  This  was  confirmed  by  deter- 
mining the  iodin  absorption  which  was  found  to  be  115.5  percent. 

A  large  quantity  of  corn  oil,  including  samples  from  four  different 
sources3,  was  then  secured  in  order  to  make  a  more  thorough  investiga- 
tion. The  oil  is  obtained  as  a  by-product  in  the  manufacture  of  corn- 
starch  and  glucose-sugar,  and  all  of  the  samples  secured  were  of  a  pale 
straw  color  and  evidently  fresh  and  pure. 

Specific  Gravity. — Three  of  these  samples  of  corn  oil  were  sufficient 
in  quantity  to  enable  me  to  make  determinations  of  their  specific  gravity 
by  means  of  a  delicate  Westphal  balance  which  by  trial  gave  the  specific 
gravity  of  pure  water  at  15°  as  i.oooo.  The  samples  of  oil  gave  the 

following  results: 

T.  2.  3. 

Specific  gravity ....    (15°)       0.9245        0.9262        0.9258 


1Journal  American  Chemical  Society  (1898)  20,  309 

2Smith  has  found  the  solubility  of  corn  oil  in  alcohol  by  volume  to  be  2  per 
cent,  at  16°  and  13  per  cent,  at  63°. 

3Samples  of  corn  oil  were  very  kindly  furnished  me  by  President  Wm.  F.  Piel, 
Jr.,  of  The  National  Starch  Manufacturing  Company,  New  York  City;  by  The  Chas. 
Pope  Glucose  Company,  Geneva,  111.;  by  The  Glucose  Sugar  Refining  Company, 
Chicago;  and  by  Messrs.  Elbert  and  Gardner,  New  York  City. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  1 71 

Melting  Point. — Preliminary  experiments  confirmed  the  observation 
of  Smith  that  the  oil  is  still  fluid  at  — 20°,  a  temperature  of  — 23° 
(obtained  with  snow  and  concentrated  sulfuric  acid)  failing  to  solidify 
the  oil.  It  was  found,  however,  that  the  oil  became  hard  and  solid  at 
about  — 36°. 

The  melting  point  was  determined  by  a  modification  of  the  method 
of  the  Association  of  Official  Agricultural  Chemists1. 

In  a  tall  beaker  of  about  2.5  liters  capacity  was  placed  a  small 
quantity  of  concentrated  sulfuric  acid  (to  absorb  water  vapor  so  that 
the  apparatus  would  remain  transparent  at  low  temperatures).  A  second 
beaker  of  about  2  liters  capacity  was  placed  in  the  first,  being  sup- 
ported by  the  rim  without  touching  the  bottom.  A  i -liter  beaker  taller 
than  the  second  was  placed  in  the  latter  and  filled  with  alcohol,  the 
space  between  the  two  being  filled  with  solid  carbon  dioxid.  A  glass 
tube  30  mm.  in  diameter  and  closed  at  the  bottom  was  fitted  into  the 
inner  beaker  with  a  large  cork,  the  tube  being  about  one-third  filled 
with  a  mixture  of  x  volume  of  concentrated  sulfuric  acid  and  3  volumes 
of  absolute  alcohol,  and  then  nearly  completely  filled  with  absolute 
alcohol.  The  temperature  of  the  alcohol  in  the  beaker  was  kept 
uniform  throughout  by  constant  stirring  with  a  wire  which  passed 
through  the  cork  and  terminated  in  a  ring  surrounding  the  glass  tube. 
A  heavy  glass  spoon  and  a  glass  spatula  were  placed  in  the  alcohol. 

When  the  temperature  reached  — 50°,  the  spoon  was  removed  and 
a  drop  of  the  oil  at  once  let  fall  upon  it.  A  thin,  solid,  white,  opaque 
disc  formed  and  was  quickly  made  to  drop  into  the  inner  tube  by  using 
the  glass  spatula.  The  disc  of  solidified  oil  settled  through  the  absolute 
alcohol  to  the  denser  liquid  below  and  th^ere  remained  in  suspension. 

The  beaker  which  had  contained  carbon  dioxid  was  replaced  by 
another  and  the  temperature  allowed  to  slowly  rise.  An  alcohol  ther- 
mometer was  used  for  reading  the  temperatures  below  the  freezing 
point  of  mercury.  Above  — 38°  a  delicate  mercury  thermometer  was 
employed. 

As  the  temperature  rose  the  disc  remained  unchanged  until  at  — 19° 
it  began  to  lose  its  opacity.  At  — 14°  it  had  become  perfectly  trans- 
parent, but  no  change  in  shape  could  be  detected  below  — 7°.  The 
disc  was  much  contracted  and  thickened  at  — 5°  and  became  entirely 
symmetrical  in  form  at  — 2.3°.  A  second  determination  gave  practically 
the  same  results,  the  final  reading  being  — 2.4°.  The  change  in  temper- 
ature (when  near  the  melting  point)  required  5  to  6  minutes  for  one 
degree. 

To  determine  the  change  in  the  consistency  of  the  oil,  a  thin-wall 
tube  of  8  mm.  diameter,  closed  at  the  bottom,  and  containing  i  cm.  of 


'U.  S.  Dept.  of  Agr.,  Div.  of  Chem.  Bui.  (1895)  46,  34. 


172  BULLETIN    NO.     53.  \_Jl<fy, 

the  oil,  was  placed  in  alcohol  at  — 45°.  After  the  oil  had  become  solid  a 
glass  rod  20  cm.  long  and  2  mm.  thick  (the  lower  end  being  widened  to 
5  mm.  diameter)  was  placed  in  the  tube  so  that  its  weight  was  entirely 
supported  by  the  solidified  oil.  At  — 13°  the  oil  had  become  trans- 
parent but  still  supported  the  rod.  At  — 10°  the  rod  began  to  settle 
appreciably  and  at  — 9°  it  had  passed  through  the  centimeter  of  oil  to 
the  bottom,  although  a  disc  of  oil  suspended  beside  the  tube  in  the 
same  liquid  had  not  changed  appreciably  in  shape.  The  change  of 
temperature  from  — ioc  to  — 9°  required  5  minutes. 

lodin  Absorption. — The  method  of  Hiibl1  was  employed  for  this 
determination,  except  for  certain  details  of  the  process. 

Standard  sodium  thiosulfate  solution  was  prepared  by  dissolving 
47.2  gms.  of  the  crystallized  salt  (Na2  S2O3  sH^O)  in  water  and  diluting 
to  2-liters.  From  theory  i  cc.  of  this  solution  should  be  equivalent  to 
12.06  mgs.  of  iodin  if  the  salt  were  pure2.  The  solution  was  standard- 
ized with  resublimed  iodin  with  the  following  results: 

Iodin  taken ...     0.5160  0.5574  gms- 

Thiosulfate  solution  required 42.9  46.4        cc. 

Iodin  equivalent  to  i  cc 12.03  12.01       mgs. 

The  average  of  these  results,  12.02,  was  used  in  the  following 
work: 

The  iodin  solution,  containing  50  gms.  iodin  and  60  gms.  mercuric 
chlorid  in  2  liters  of  alcohol,  was  standardized  whenever  used. 

Little  pipettes  of  about  0.5  cc.  capacity  were  placed  in  5  cc.  vials 
nearly  filled  with  the  corn  oil,  the  bulb  of  the  pipette  being  immersed, 
and  the  whole  weighed.  The  measure  of  oil  was  then  transferred  to  a 
500  cc.  glass  stoppered  bottle,  the  pipette  returned  to  the  vial,  and  the 
exact  weight  of  oil  taken  determined  by  difference.  The  duplicate  is 
taken  immediately  and  necessitates  only  one  more  weighing.  10  cc.  of 
chloroform  and  40  cc.  of  iodin  solution  were  added  to  the  oil.  After 
2  hours  25  cc.  of  10  per  cent,  potassium  iodid  solution  and  about  125 
cc.  of  water  were  added  and  the  excess  of  iodin  determined  by  titrating 
with  the  sodium  thiosulfate  solution,  starch  indicator  being  added  near 
the  close  of  the  reaction. 

Duplicate  determinations  of  four  different  samples  of  oil  from  as 
many  different  sources  gave  the  following  results: 


journal  Society  Chemical  Industry  (1884)  3,  641. 

button's  Volumetric  Analysis,  (1890)  115,  states  that  standard  sodium  thiosul- 
fate solution  may  be  made  by  simply  dissolving  an  exact  weight  of  the  crystallized 
salt,  Na2  S2O3  5H2O,  in  water  and  diluting  to  a  definite  volume. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  173 

Oil  taken.  lodin  absorbed.  lodin  absorbed. 

gms.          gms.         per  cent, 
jo. 3473        0.4255        122.5 
"  |  0.3844        0.4729        123.0 

(0.4251  0.5179  !21.8 

"I  0.4714        0.5729        121. 5 

j  0.4281        0.5212        121.7 
'•  \  0.4742       0.5772       121.7 

(0.4326       0.5324       123.1 

"I  0.5168  0.6351  122.9 

Oxygen  Absorption. — In  order  to  afford  a  large  surface  for  the 
absorption  of  oxygen,  the  oil  was  placed  in  a  low  crystallizing  dish  of 
75  mm.  diameter.  This  was  allowed  to  stand  at  the  room  temperature, 
the  weight  of  the  oil  being  determined  from  time  to  time  as  follows: 

Weight  of  oil  taken •. 2 . 1732  gms. 

Weight   after  i  day   2.1722     " 

"  "      7  days 2.1718     " 

ii      "   2.1718     " 

"       12       "     2.1718       " 

These  results  confirm  those  of  Spiiller,  showing  that  the  oil  does 
not  take  up  oxygen  under  these  conditions. 

The  dish  was  then  placed  in  a  water  oven  and  the  following  data1 
obtained: 

Weight  after  i  hour 2 . 1726  gms. 

' '      i  day   2 . 1996 

"      2  days 2.2488      " 

3     •'     2.2590  " 

"      4     "    2.2588  " 

"      5     "    2.2558  " 

"           "      6     "       2.2513 

"      7     "    2.2448  " 

The  first  action  of  air  upon  the  hot  oil  is  evidently  the  direct  addi- 
tion of  oxygen;  but  after  2  or  3  days  the  oil  began  to  turn  noticeably 
darker  in  color  and  finally  to  lose  weight,  evidently  due  to  a  secondary 
reaction  which  effects  some  decomposition  of  the  oil  with  formation  of 
volatile  products. 

Lecithin1.—  A  weighed  quantity  of  oil  was  mixed  with  potassium 
nitrate  and  sodium  carbonate  in  a  platinum  dish  and  ignited  until  the 
carbon  was  completely  burned.  The  fused  mass  was  dissolved  in  dilute 

'These  results  emphasize  the  importance  of  avoiding  the  presence  of  oxygen  in 
drying  corn  or  corn  oil  in  analytical  work. 

'-'Lecithin  is  commonly  regarded  as  a  compound  of  the  base,  neurine,  with  di- 
stearyl-glycero-phosphoric  acid,  although  one  or  both  of  the  stearic  acid  radicals  may 
be  replaced  by  radicals  of  palmitic  or  oleic  acid,  and  the  neurine  (trimethylhydroxy- 
ethyl  ammonium  hydroxid)  is  sometimes  replaced  by  another  base;  e.  g.,  betaine. 


174  BULLETIN    NO.     53.  \_Jufyi 

hydrochloric  acid,  and  the  total  phosphoric  acid  determined1.  The 
amount  of  lecithin  was  calculated  by  multiplying  the  weight  of  mag- 
nesium pyrophosphate  obtained  by  the  factor  7.25*.  Duplicate  deter- 
minations gave  the  following  results  : 

Oil  taken 10.728  6.435     gms. 

KNO3  used3 10.0  35.0 

Mg2P2O7  obtained 0.0221  0.0132     " 

Lecithin o .  1602  o .  0957     ' ' 

Lecithin  in  oil4 1.49  1.49     percent. 

Cholesterol^. — To  determine  cholesterol6  about  50  gms.  of  the  oil 
were  saponified  on  the  water  bath  with  20  gms.  of  potassium  hydroxid 
and  100  cc.  of  70  per  cent,  alcohol.  The  soap  was  transferred  to  a 
large  separatory  funnel  with  200  cc.  of  water  and  shaken  first  with  500 
cc.  of  ether  and  then  3  times  with  250  cc.  of  ether.  The  four  portions 
of  separated  ether  were  combined,  and  the  ether  distilled,  the  residue 
being  resaponified  with  2  gms.  of  potassium  hydroxid  and  10  cc.  of  70 
per  cent,  alcohol.  The  solution  was  then  transferred  to  a  small  sep- 
aratory funnel  with  20  cc.  of  water  and  shaken  with  100  cc.  of  ether. 
After  separating  the  aqueous  layer  the  ether  solution  was  washed  four 
times  with  10  cc.  of  water,  the  ether  solution  being  finally  transferred 
to  a  weighed  flask,  the  ether  distilled  and  the  weight  of  the  dry  residue 
(cholesterol)  determined.  Three  determinations  gave  the  following 
results  : 

Oil  taken   50.16  53 .50  54-24       gms. 

Cholesterol  obtained 0.7002  0.7114  0.7512 

Cholesterol  in  oil 1.40  1.33  1.38      percent7 

The  cholesterol  was  recrystallized  from  absolute  alcohol  in  charac- 
teristic glistening  plates,  melting  at  137°  to  137.5°.  It  also  gave  the 
characteristic  color  reactions8  for  cholesterol  :  i,  when  shaken  with 
chloroform  and  sulfuric  acid;  2,  when  evaporated  to  dryness  with 
nitric  acid;  3,  when  warmed  with  hydrochloric  acid  and  ferric  chlorid. 


'Cf.  Hoppe-Seyler,  Jahresbericht  uber  die  Fortschritte  der  Chemie  (1866)  744; 
Schulze  and  Frankfurt,  Landwirtschaftliche  Versuchs-Stationen  (1893)  43,  207. 

27.25  parts  of  lecithin  (C44H90O9PN)yield  i  part  of  Mg2  P2  O7, 

3The  proportions  of  KNO8  used  were  purposely  varied,  but  the  results  indicate 
that  the  smaller  proportion  was  sufficient. 

4  By  extracting  corn  with  ether  and  alcohol,  successively,  Schulze  and  Frank- 
furt (reference  above)  have  obtained  amounts  of  phosphoric  acid  equivalent  to  0.25 
to  0.28  per  cent,  of  lecithin  in  the  corn. 

5 A  monatomic  alcohol,  C26H13OH. 

6Cf.  Burner,  Zeitschrift  fiir  Untersuchung  der  Nahrungs-  und  Genussmittel 
(1898)  21,  for  recent  work  on  the  details  of  this  method. 

7Spiiller  had  obtained  1.35  per  cent,  and  Hart  1.55  per  cent,  of  unsaponifiable 
matter. 

8Watt's  Dictionary  (1889)  2,  147. 


1898.]  CHEMISTRY    OF    THE    CORN    KERNEL.  175 

Total  Fatty  Acids. — After  removing  the  cholesterol  from  about  50 
gms.  of  oil  the  remaining  soap  solution  (about  500  cc.)  was  acidified 
with  hydrochloric  acid  and  shaken  in  a  separatory  funnel.  An  ethereal 
layer  of  about  150  cr.  at  once  separated.  After  adding  100  cc.  more 
ether  and  thoroughly  shaking,  the  aqueous  layer  was  drawn  off,  the 
ether  solution  of  the  fatty  acids  was  washed  with  several  portions  of 
water  and  then  transferred  to  a  weighed  flask,  the  ether  distilled  off,  a 
few  cubic  centimeters  of  absolute  alcohol  dissolved  in  the  residue  and 
evaporated  to  remove  traces  of  water,  and  the  weight  of  the  total  fatty 
acids  determined  : 

Oil  taken 50 . 160      gms. 

Fatty  acids  obtained 46.935         " 

Fatty  acids  in  oil 93-57         per  cent. 

The  fatty  acids  form  a  solid  mass  at  15°,  but  melt  nearly  com- 
pletely at  one  or  two  degrees  above,  the  last  particles  of  solid  disap- 
pearing at  23°.  Prepared  as  described  the  fatty  acids  absorbed  only 
126.4  percent,  of  iodin  instead  of  130.7  percent,  as  calculated  from  the 
iodin  absorption  of  the  oil.  This  indicates  that  oxygen  had  been  ab- 
sorbed by  the  acids  during  the  process  of  separation.  It  was  found  that 
oxygen  is  slowly  absorbed  by  the  fatty  acids  while  standing  in  a  desic- 
cator at  the  ordinary  temperature.  At  100°  the  absorption  is  much 
more  rapid  although,  as  with  the  oil,  secondary  reactions  soon  begin  at 
the  higher  temperature.  The  change  in  weight  was  found  to  be  as 
follows  : 

Time,  Weight  of  fatty  acids,  gms., 

in  days.  ,  in  desiccator.         in  water  oven. 

o i .  9685  2 . 2740 

i 1.9692  2.3106 

2 1.9717  2.3366 

3 i  -9777  2  •  3366 

4 1.9847  2.3282 

8 2.0231 

12 2. 0665 

16 2 . 091 1 

22 2.  1157 

28 2  .  1293 

34 2.1297 

All  action  apparently  ceased  after  about  one  month's  time.  A  con- 
siderable portion  of  the  fatty  acids  had  separated  in  the  solid  form  and 
of  a  pure  white  color,  while  the  other  portion  remained  a  colorless, 
oily  liquid. 

It  is  of  interest  to  note  the  apparent  relation  between  the  iodin 
absorption  and  the  oxygen  absorption  by  the  fatty  acids.  As  already 
shown  the  fatty  acids  as  prepared  absorbed  126.4  per  cent,  of  iodin. 
If  an  equivalent  amount  of  the  bivalent  oxygen  may  be  absorbed  instead 


176  BULLETIN    NO.     53. 

of  the  univalent  iodin,  then  8.0  per  cent,  of  oxygen  should  be  taken  up. 
The  results  show  that  1.9685  gms.  of  the  fatty  acids  absorbed  0.1612 
gms.  of  oxygen,  an  amount  equal  to  8.2  per  cent. 

Time  would  not  permit  the  preparation  of  the  fatty  acids  in  a 
manner  which  would  prevent  the  absorption  of  oxygen  during  the 
process,  and  then  a  repetition  of  the  quantitative  determination  of  the 
absorption.  This  is  especially  desirable  in  order  to  confirm  the  results 
as  given  above,  and  the  writer  expects  to  investigate  this  point  more 
fully  in  the  near  future. 

Volatile  Acids. — About  5  gms.  of  oil  were  saponified  in  a  500  cc. 
flask  with  2  gms.  of  potassium  hydroxid  and  40  cc.  of  80  per  cent, 
alcohol.  After  evaporating  the  last  of  the  alcohol,  100  cc.  of  recently 
boiled  water  were  added,  the  soap  solution  acidified  with  40  cc.  of  dilute 
sulfuric  acid  (i  to  10),  a  few  pieces  of  freshly  ignited  pomace  stone 
added,  the  flask  connected  with  a  condenser  by  means  of  a  safety  bulb 
tube,  and  no  cc.  of  distillate  collected.  After  mixing,  100  cc.  were 
passed  through  a  dry  filter  and  titrated  with  one-twenty-fifth  normal 
barium  hydroxid  solution. 

Four  determinations  gave  the  following  results: 

Oil  taken 4-5o6         5.894         5.671         5.718  gms. 

N/25  Ba  (OH)2  required.         1.3  1.5  1.4  1.3       cc. 

As  two  blank  determinations  required  1.3  and  1.5  cc.,  respectively, 
of  the  barium  hydroxid  solution  it  is  evident  that  the  oil  contains  no 
volatile  acids.1 

Separation  and  Determination  of  Fatty  Acids. — It  has  been  found 
especially  by  Hazura2  and  his  associates  that  the  oxidation  of  unsatu- 
rated  fatty  acids  by  alkaline  potassium  permanganate  serves  as  a  basis 
for  the  approximate  separation  of  several  fatty  acids.  Under  proper 
conditions  the  oxidation  is  chiefly  confined  to  the  direct  addition  of  the 
hydroxyl  group  (OH)  wherever  "  free  valences  "  exist.  The  following 
shows  the  relations  among  several  acids  in  the  series  containing  eighteen 
'atoms  of  carbon  in  the  molecule3: 

Unsaturated  Acids.  Saturated  Acids. 

Stearic,  C1BH36O2. 

Oleic,  C,8H34O.j,  oxidizes  to. ..  .dihydroxy  stearic,  C18H34(OH)2O2. 
Linolic,  Cj8H32O2,  oxidizes  to.  . tetrahydroxy  stearic,  C.18H3.j(OH)4O.j. 
Linolenic,  C,8H30O2,  oxidizes  to.hexahydroxy  stearic,  C18H30(OH)6O2. 


1Spiiller  gives  Reichert's  number  for  the  volatile  acids  as  0.33;  Smith  states 
that  the  oil  examined  by  him  contained  volatile  acids  equivalent  to  0.56  per  cent,  of 
KOH;  and  Morse  (New  Hampshire  Experiment  Station  Bulletin  (1892)  16,  19)  gives 
volatile  acids  as  3.2  per  cent,  in  a  sample  of  corn  oil  which  absorbed  112.8  per  cent, 
of  iodin. 

2Monatshefte  fur  Chemie  (1886)  to  (1889),  Vols.  7  to  10. 

3Cf.  Hazura,  ibid.     (1887)  8,  269. 


1898.]  CHEMISTRY    OF   THE    CORN    KERNEL.  177 

After  removing  the  cholesterol  from  53.5  gins,  of  oil,  the  combined 
soap  solution  was  heated  till  the  dissolved  ether  was  distilled,  cooled, 
and  diluted  to  2  liters.  Two  liters  of  a  1.5  per  cent,  potassium 
permanganate  solution  were  then  gradually  added  with  constant  stirring. 
After  10  minutes  the  precipitated  manganese  hydroxid  was  filtered  off, 
and  the  clear  filtrate  acidified  with  hydrochloric  acid.  The  precipitate 
thus  formed  wa?  filtered  off,  washed,  air-dried,  and  then  extracted  with 
ether.  The  residue  insoluble  in  ether  weighed,  after  drying,  18  gms. 
It  was  extracted  with  boiling  water  until  but  2  gms.  remained,  which 
when  again  extracted  with  ether,  left  a  residue  of  only  0.6  gm.  and 
soluble  in  boiling  water. 

The  substance  dissolve4  in  hot  water  was  practically  completely 
precipitated  as  the  solution  cooled1  and  proved  to  be  sativic  acid 
(tetrahydroxy  stearic  acid),  as  is  indicated  by  the  method  of  formation 
and  by  its  solubility  in  hot  water.  The  melting  point2  of  the  dried  sub- 
stance was  i57c-i59°- 

The  quantitative  synthesis  of  the  potassium  salt  was  effected  by 
dissolving  a  weighed  amount  of  the  acid  in  warm  alcohol  and  titrating 
with  standard  alcoholic  potassium  hydroxid  solution: 

Sativic  acid         Potassium  hydroxid      Per  cent,  potassium      Per  cent,  potassium 
taken.  required.  in  product.3  (theory)  4 

i.ooo  0.1604  10.08  10.14 

The  ether  solutions  obtained  as  described  above  were  combined 
and  the  ether  distilled.  The  residue  was  solid  at  the  room  temperature, 
melted  gradually  as  the  temperature  rose  from  40°  to  60°,  and  was 
found  to  absorb  79.2  per  cent,  of  iodin,  thus  showing, very  incomplete 
oxidation  of  the  unsaturated  acids. 

A  second  lot  of  corn  oil  (54.24  gms.)  was  oxidized  by  alkaline 
permanganate,  the  cholesterol  and  then  the  dissolved  ether  having  been 
previously  removed.  Tne  soap  was  diluted  to  2  liters  and  cooled  to  o° 
by  ice  kept  in  the  solution.  A  solution  of  potassium  permanganate 
containing  80  gms  in  2  liters  of  water  was  slowly  added  with  constant 
stirring.  After  30  minutes  precipitated  matter  was  filtered  off  and. 
washed;  the  clear  filtrate  was  acidified  with  150  cc.  of  concentrated 
hydrochloric  acid;  the  precipitated  acids  were  filtered  off,  dried,  and 
extracted  with  ether.  The  residue  insoluble  in  ether  (17.7  gms.)  was 


'2000  cc  of  the  filtrate  from  the  precipitated  sativic  acid  required  only  0.5  cc.  of 
N  5  KOH  to  show  alkalinity  with  phenol  phthalein. 

2 Bauer  and  Hazura,  Monatshefte  fur  Chemie  (1886)  7,  225,  give  160°  as  the 
melting  point  of  several  samples  of  sativic  acid,  prepared  in  a  manner  similar  to 
the  above. 

3Calculated  weight  =  i  .000-)-  o.  1604  — 

56 . 14° 
^ForC18H31(OH)4  O.K. 


178  BULLETIN    NO.    53.  [/"()'> 

dissolved  in  boiling  95  per  cent,  alcohol.  On  cooling,  the  sativic  acid 
separated  in  the  crystalline  form,  melting  at  161^-16$  . 

By  distilling  the  ether  from  the  solution  obtained  as  above 
described,  a  brown  residue  (9.5  gms.)  was  obtained  which  melted  at  55° 
to  60°  and  showed  an  iodin  absorption  of  only  9.2  per  cent. 

The  aqueous  acid  solution  from  which  the  insoluble  organic  acids 
had  been  precipitated  by  hydrochloric  acid  was  evaporated  nearly  to 
dryness,  a  black  tarry  mass  gradually  separating,  showing  that,  although 
a  small  amount  of  unsaturated  acids  had  been  unacted  upon,  the  oxida- 
tion had  gone  far  beyond  the  simple  addition  of  hydroxyl  groups  to  the 
unsaturated  compounds. 

To  further  investigate  the  fatty  acids,  a  method  essentially  that  of 
Muter1  was  tried  for  their  separation  and  determination.  It  is  based 
upon  the  fact  that  the  lead  salts  of  the  unsaturated  acids,  oleic,  linolic, 
etc.,  are  soluble  in  ether;  while  the  lead  salts  of  the  saturated  acids, 
stearic,  palmitic,  etc.,  are  not. 

About  1.5  gms.  of  the  oil  were  saponified  with  alcoholic  potash  and 
the  soap  dissolved  in  water,  the  unsaponifiable  substance  (cholesterol) 
being  separated  from  the  soap  solution  by  shaking  with  ether.  The 
solution  was  then  neutralized  with  acetic  acid,  and  the  fatty  acids  pre- 
cipitated with  lead  acetate,  a  slight  excess  being  added.  The  lead  salts 
were  washed  with  water,  and  then  transferred  with  50  cc.  of  ether  to  a 
glass  cylinder  of  about  60  cc.  capacity,  which  was  stoppered  and  then 
violently  shaken  for  5  to  10  minutes.  The  small  quantity  of  matter  in- 
soluble in  ether  was  then  allowed  to  settle.  A  stopper  carrying  two 
glass  tubes  similar  to  those  used  in  the  ordinary  washing  bottle  was 
placed  in  the  cylinder,  the  long  tube  reaching  nearly  to  the  undissolved 
sediment.  By  blowing  in  the  short  tube  the  clear  solution  is  transferred 
almost  completely  without  disturbing  the  sediment.  The  undissolved 
substance  was  then  shaken  with  more  ether,  allowed  to  settle,  and  the 
ether  transferred  as  before  as  completely  as  possible.  This  treatment 
was  twice  more  repeated.  The  undissolved  lead  salt  was  then  warmed 
with  about  25  cc.  of  dilute  hydrochloric  acid,  till  the  fatty  acids  sep- 
arated; and,  after  cooling  sufficiently  the  whole  was  transferred  to  a  250 
cc.  graduated  bulb  tube,  ether  being  used  to  complete  the  transfer. 
The  portion  of  the  tube  below  the  bulb  contained  50  cc.  and  was 
graduated  to  0.2  cc.  A  small  glass  tube  carrying  a  stopcock  was  sealed 
in  just  below  the  50  cc.  mark.  The  tube  was  filled  to  the  250  cc.  mark 
(above  the  bulb)  with  ether,  and  thoroughly  shaken.  The  aqueous 
layer,  containing  the  excess  of  hydrochloric  acid  and  the  precipitated 
lead  chlorid  was  allowed  to  separate. 

The  volume  of  ether  solution  was  observed,  and  200  cc.  of  it  were 


Analyst  (1877)  2,  73. 


1898.]  CHEMISTRY  OF  THE  CORN  KERNEL.  179 

drawn  off  into  a  weighed  flask,  evaporated  to  dryness,  and  the  weight  of 
the  residue  determined. 

Duplicate  determinations  gave  the  following  : 

Oil  taken 1.600  1.610      gms. 

Volume  of  ether  solution  222 .4  221  .o          cc. 

Ether  solution  taken 200.0  200.0           cc. 

Saturated  acids  obtained 0.0670  0.0648    gms. 

Saturated  acids  in  oil 4 . 66  4-44     Per  cent. 

The  residue  of  saturated  acids  formed  a  white  solid  mass.  It  was 
dissolved  in  hot  alcohol  and  allowed  to  crystallize.  The  melting  point 
was  57°.  The  quantity  of  the  saturated  acids  thus  obtained  was  con- 
sidered too  small  for  further  satisfactory  examination  (see  foot  note 
below). 

Before  the  lead  salts  of  the  saturated  acids  were  completely  washed 
by  decantation1  the  clear  ether  solution  of  the  lead  salts  of  the  unsat- 
urated  acids  absorbed  oxygen,  and  became  cloudy,  a  white  precipitate' 
forming  in  considerable  amount.  Two  samples  of  the  atmosphere  in 
the  cylinders  above  the  solutions  were  drawn  off  in  gas  burettes;  and, 
after  removing  the  ether  vapor,  the  residual  air  was  found  to  contain 
only  15.3  per  cent,  and  13.9  per  cent.,  respectively,  of  oxygen  instead 
of  20.8  per  cent,  as  found  in  the  air  of  the  laboratory. 

By  subtracting  the  percentage  (4.55)  of  saturated  acids  found  in 
the  oil  from  that  of  the  total  fatty  acids  (93.57)  the  amount  of  total 
unsaturated  acids  is  found  to  be  89.02  per  cent.,  consisting  of  oleic 
and  linolic  acids.  (The  melting  point  of  the  sativic  acid  obtained  and 
the  composition  of  its  potassium  salt  prove  the  absence  of  linusic  acid 
in  the  products  of  oxidation,  and,  hence,  of  linolenic  acid  in  the  total 
fatty  acids.) 

From  the  iodin  absorption,  the  amounts  of  oleic  and  linolic  acids 
can  be  accurately  determined.  Thus: 

Oleic  acid,      C18H34O2  -|-  I,  =  CtHH34I2O2,  diiodo  stearic  acid. 
Linolic  acid,  ClaH32O2  -j-  2l2  =  C1BH3.jl4O2,  tetraiodo  stearic  acid. 

As  89.02  gms.  of  these  unsaturated  acids  in  the  ratio  in  which  they 
exist  in  corn  oil  absorb  122.3  gms.  of  iodin,  the  following  equation  can 
be  stated,  x  being  the  number  of  gms.  of  oleic  acid: 

254  508 


'At  least  two  days'  time  is  required  for  this  process,  and  even  this  was  found 
more  satisfactory  than  filtration.  I  have  no  doubt  that,  if  centrifugal  force  were 
substituted  for  gravity,  the  washing  by  decantation  could  be  done  much  better  and  so 
quickly  that  the  unsaturated  acids  could  also  be  determined  before  the  absorption  of 
any  appreciable  amount  of  oxygen.  Quantities  of  the  separated  materials  sufficient 
for  further  examination  could  doubtless  be  obtained  in  a  short  time.  No  suitable 
centrifuge  was  at  hand  for  this  work. 


l8o  BULLETIN    NO.     53.  LA^'>    1898. 

The  oleic  acid  is  found  to  be  42.92  gms.  and  the  linolic  acid  46.10 
gms. 

By  subtracting  from  the  amount  of  saturated  acids  the  equivalent 
of  the  -stearic  acid  contained  in  the  lecithin,  and  calculating  to  the 
respective  glycerol  esters  the  remaining  saturated  acids  (as  stearic  acid), 
the  oleic  acid,  and  the  linolic  acid,  the  following  summary  is  obtained 
as  the  composition  of  the  oil  of  corn: 

Cholesterol i .  37  per  cent. 

Lecithin 1.49     "      " 

Stearin  (?) 3.66     " 

Olein 44 . 85     " 

Linolin ;   48.19     " 


Total 99 . 56 

C.  G.  HOPKINS,  PH.  D.,    Chemist. 


WCA 


UNIVERSITY  OF  ILLINOIS-URBANA 


